This is an issue I and my coworker have been having with previous versions of INDD CC, along with 2021 (16.1). It's been a problem for about a year now. We work off of a server, and exporting to a PDF fails frequently. It usually works if we export to our desktops, but exporting to the server is very hit-or-miss. It doesn't matter if the file is older or has just been created, and it doesn't matter whether it contains linked files or not.

I have never had it fail to export to my desktop, but she has. She had to reboot her computer before she could get a PDF out of it.

We're both on Mac OS Mojave 10.14.6.