Fix for this issue is now available in the latest update of InDesign 2020 – that is, InDesign 15.0.1
In the Creative Cloud Desktop application, click on the Updates section on the left. You should be able to see the Update available for InDesign. Please update your InDesign application to this version to try out the fix.
Let us know in the comments section if you face any problem with the updation process.
Adobe InDesign TeamKB commented
I am also having with CC 2019
it doesnt matter if i export 1 page or the entire document, it succesfully create the pdf, then hangs, indesign is totally unresponsive, no errors.
i have to end task and recover the document each time, thankfully i have lost enough work over the years to have multiple back ups, but not good.