Well, would have been too easy anyway 
I assume you didn’t configure the pdfexport module to use a remote instance of google chrome. I’d like you to try this as well, in order to check if it makes a difference.
To set this up, go to Configuration
→ Modules
→ pdfexport
→ Chrome
(Tab). There define 127.0.0.1
as remote host and leave the default port.
Then launch google chrome manually using the following commandline: google-chrome --remote-debugging-address=127.0.0.1 --remote-debugging-port=9222 --headless --keep-alive-for-test --disable-gpu --disable-dev-shm-usage --no-sandbox --bwsi --no-first-run --user-data-dir=/tmp --homedir=/tmp
The browser should then keep running and give output similar to this: DevTools listening on ws://127.0.0.1:9222/devtools/browser/726847aa-14cf-4189-8d30-3d70c588d565
Then start the export again and check the result.
Oh and please include the debug log that’s the result of this in any case. I’d like to see something like the following:
NOTICE: PHP message: icingaweb2: DEBUG - Transmitting CDP call: Target.createTarget(url)
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP result: targetId
NOTICE: PHP message: icingaweb2: DEBUG - Transmitting CDP call: Log.enable()
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP result: none
NOTICE: PHP message: icingaweb2: DEBUG - Transmitting CDP call: Network.enable()
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP result: none
NOTICE: PHP message: icingaweb2: DEBUG - Transmitting CDP call: Page.enable()
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP result: none
NOTICE: PHP message: icingaweb2: DEBUG - Transmitting CDP call: Console.enable()
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP result: none
NOTICE: PHP message: icingaweb2: DEBUG - Transmitting CDP call: Page.setDocumentContent(frameId,html)
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Page.documentOpened(frame={"id":"3663F5C8A7F8BB9B9B191C045439F07D","loaderId":"9357875934821045222C944AB98E1742","url":"about:blank","domainAndRegistry":"","securityOrigin":":\/\/","mimeType":"text\/html","adFrameType":"none","secureContextType":"InsecureScheme","crossOriginIsolatedContextType":"NotIsolated","gatedAPIFeatures":["SharedArrayBuffers","SharedArrayBuffersTransferAllowed"]})
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Network.requestWillBeSent(requestId="644.1",loaderId="9357875934821045222C944AB98E1742",documentURL="about:blank",request={"url":"http:\/\/localhost\/icingaweb2\/public\/img\/icinga-logo-big-dark.png","method":"GET","headers":{"sec-ch-ua":"","Referer":"","sec-ch-ua-mobile":"?0","User-Agent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) HeadlessChrome\/90.0.4430.212 Safari\/537.36"},"mixedContentType":"none","initialPriority":"Low","referrerPolicy":"strict-origin-when-cross-origin"},timestamp=2556.020359,wallTime=1620713836.916623,initiator={"type":"parser","url":"about:blank","lineNumber":46365,"columnNumber":15},type="Image",frameId="3663F5C8A7F8BB9B9B191C045439F07D",hasUserGesture=false)
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Network.requestWillBeSent(requestId="644.2",loaderId="9357875934821045222C944AB98E1742",documentURL="about:blank",request={"url":"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAV4AAADICAIAAAAvAR6nAAAABmJLR0QA\/wD\/AP+gvaeTAAAX1UlE%0AQVR4nO3de1xUZf4H8O+ZO3MDHEAZFUFuGlgphCDkJdcspbCLppW\/1nZJV91XN90NTNYiy03NxMuu%0AGGW31yttX2tReQv7ZW4ZKikqoiaIkCgXheEyMHNm5vz+ODo7P2ZkkBlBD5\/3X8fvPM\/MM\/OKb+c8...","method":"GET","headers":{"Referer":"","User-Agent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) HeadlessChrome\/90.0.4430.212 Safari\/537.36"},"mixedContentType":"none","initialPriority":"Low","referrerPolicy":"strict-origin-when-cross-origin"},timestamp=2556.020788,wallTime=1620713836.917052,initiator={"type":"parser","url":"about:blank","lineNumber":46365,"columnNumber":15},type="Image",frameId="3663F5C8A7F8BB9B9B191C045439F07D",hasUserGesture=false)
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Network.requestServedFromCache(requestId="644.2")
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Network.responseReceived(requestId="644.2",loaderId="9357875934821045222C944AB98E1742",timestamp=2556.020903,type="Image",response={"url":"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAV4AAADICAIAAAAvAR6nAAAABmJLR0QA\/wD\/AP+gvaeTAAAX1UlE%0AQVR4nO3de1xUZf4H8O+ZO3MDHEAZFUFuGlgphCDkJdcspbCLppW\/1nZJV91XN90NTNYiy03NxMuu%0AGGW31yttX2tReQv7ZW4ZKikqoiaIkCgXheEyMHNm5vz+ODo7P2ZkkBlBD5\/3X8fvPM\/MM\/OKb+c8...","status":200,"statusText":"OK","headers":{"Content-Type":"image\/png"},"mimeType":"image\/png","connectionReused":false,"connectionId":0,"fromDiskCache":false,"fromServiceWorker":false,"fromPrefetchCache":false,"encodedDataLength":0,"protocol":"data","securityState":"unknown"},frameId="3663F5C8A7F8BB9B9B191C045439F07D")
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Network.dataReceived(requestId="644.2",timestamp=2556.020917,dataLength=6176,encodedDataLength=0)
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Network.loadingFinished(requestId="644.2",timestamp=2556.020918,encodedDataLength=0,shouldReportCorbBlocking=false)
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Network.requestWillBeSent(requestId="644.3",loaderId="9357875934821045222C944AB98E1742",documentURL="about:blank",request={"url":"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAV4AAADICAIAAAAvAR6nAAAABmJLR0QA\/wD\/AP+gvaeTAAAO1ElE%0AQVR4nO3deUxUV\/\/H8TMz7AzDDCgCNYKs1qJUQUEJbgUxaupg3RpsEBO0KcRScQOrVikuRUEJgmjU%0AVNOkS6qtSeuGTatpK20JQUVrq1StC6sIKogww++P+3smPCwz9hGhA+\/XX+d+7+dc70zk5M7MvecI...","method":"GET","headers":{"Referer":"","User-Agent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) HeadlessChrome\/90.0.4430.212 Safari\/537.36"},"mixedContentType":"none","initialPriority":"Low","referrerPolicy":"strict-origin-when-cross-origin"},timestamp=2556.0211,wallTime=1620713836.917364,initiator={"type":"parser","url":"about:blank","lineNumber":46365,"columnNumber":15},type="Image",frameId="3663F5C8A7F8BB9B9B191C045439F07D",hasUserGesture=false)
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Network.requestServedFromCache(requestId="644.3")
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Network.responseReceived(requestId="644.3",loaderId="9357875934821045222C944AB98E1742",timestamp=2556.021161,type="Image",response={"url":"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAV4AAADICAIAAAAvAR6nAAAABmJLR0QA\/wD\/AP+gvaeTAAAO1ElE%0AQVR4nO3deUxUV\/\/H8TMz7AzDDCgCNYKs1qJUQUEJbgUxaupg3RpsEBO0KcRScQOrVikuRUEJgmjU%0AVNOkS6qtSeuGTatpK20JQUVrq1StC6sIKogww++P+3smPCwz9hGhA+\/XX+d+7+dc70zk5M7MvecI...","status":200,"statusText":"OK","headers":{"Content-Type":"image\/png"},"mimeType":"image\/png","connectionReused":false,"connectionId":0,"fromDiskCache":false,"fromServiceWorker":false,"fromPrefetchCache":false,"encodedDataLength":0,"protocol":"data","securityState":"unknown"},frameId="3663F5C8A7F8BB9B9B191C045439F07D")
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Network.dataReceived(requestId="644.3",timestamp=2556.021173,dataLength=3871,encodedDataLength=0)
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Network.loadingFinished(requestId="644.3",timestamp=2556.021175,encodedDataLength=0,shouldReportCorbBlocking=false)
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Network.requestWillBeSent(requestId="644.44",loaderId="9357875934821045222C944AB98E1742",documentURL="about:blank",request={"url":"http:\/\/localhost\/img\/icinga-loader.gif","method":"GET","headers":{"sec-ch-ua":"","Referer":"","sec-ch-ua-mobile":"?0","User-Agent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) HeadlessChrome\/90.0.4430.212 Safari\/537.36"},"mixedContentType":"none","initialPriority":"Low","referrerPolicy":"strict-origin-when-cross-origin"},timestamp=2556.032279,wallTime=1620713836.928543,initiator={"type":"parser","url":"about:blank","lineNumber":46365,"columnNumber":15},type="Image",frameId="3663F5C8A7F8BB9B9B191C045439F07D",hasUserGesture=false)
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Page.domContentEventFired(timestamp=2556.033097)
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP result: none
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Network.resourceChangedPriority(requestId="644.44",newPriority="High",timestamp=2556.040863)
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Network.resourceChangedPriority(requestId="644.1",newPriority="High",timestamp=2556.040874)
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Network.loadingFailed(requestId="644.1",timestamp=2556.079289,type="Image",errorText="net::ERR_CONNECTION_REFUSED",canceled=false)
NOTICE: PHP message: icingaweb2: ERROR - Headless Chrome was unable to complete a request to "http://localhost/icingaweb2/public/img/icinga-logo-big-dark.png". Error: net::ERR_CONNECTION_REFUSED
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Log.entryAdded(entry={"source":"network","level":"error","text":"Failed to load resource: net::ERR_CONNECTION_REFUSED","timestamp":1620713836975.5608,"url":"http:\/\/localhost\/icingaweb2\/public\/img\/icinga-logo-big-dark.png","networkRequestId":"644.1"})
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Network.loadingFailed(requestId="644.44",timestamp=2556.079452,type="Image",errorText="net::ERR_CONNECTION_REFUSED",canceled=false)
NOTICE: PHP message: icingaweb2: ERROR - Headless Chrome was unable to complete a request to "http://localhost/img/icinga-loader.gif". Error: net::ERR_CONNECTION_REFUSED
NOTICE: PHP message: icingaweb2: DEBUG - Transmitting CDP call: Page.printToPDF(headerTemplate,footerTemplate,transferMode,printBackground)
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Log.entryAdded(entry={"source":"network","level":"error","text":"Failed to load resource: net::ERR_CONNECTION_REFUSED","timestamp":1620713836975.719,"url":"http:\/\/localhost\/img\/icinga-loader.gif","networkRequestId":"644.44"})
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Page.loadEventFired(timestamp=2556.07958)
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Page.frameResized()
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP event: Page.frameResized()
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP result: data
NOTICE: PHP message: icingaweb2: DEBUG - Transmitting CDP call: Target.closeTarget(targetId)
NOTICE: PHP message: icingaweb2: DEBUG - Received CDP result: success
NOTICE: PHP message: icingaweb2: DEBUG - Failed to close browser connection: Empty read; connection dead? Stream state: {"timed_out":false,"blocked":true,"eof":true,"stream_type":"tcp_socket\/ssl","mode":"r+","unread_bytes":0,"seekable":false}