Thank you for your support. The issue is now fixed in the latest update of InDesign.
Please upgrade to the new InDesign 14.0 from your Creative Cloud Application.
If you are unable to see the update yet, click on the menu (three dots) on the top right corner of Creative cloud app and click on “Check for App Updates”.
Let us know your feedback in the comment section.
InDesign TeamKenn commented
That is not the case on my iMac 27" 2017. I have all files stored locally.
Every second time I make an PDF print export, the background indicator just keep spinning and spinning. I can't cancel the task - neither close the document (thus it is working in the background). So a force quit will do, and the first time the export wil work just fine. The second time it fails ...