Debugging

Follow these instructions, if Blender crashes immedietley upon opening a file. This is called “a crash on load” in liboverride resync code.

Found and fixed in main a (potentially) related issue.
File is still broken, not sure why, but it currently makes auto resync of overrides completely freak out.
When this happen, easy work around is to:

Disable TEMPORARILY auto-resync (preferences-> Experimental -> Debugging -> Override Auto Resync)
Open the broken file
Manually resync the overrides one by one (right-click on top-level collections in the outliner, Library Override -> Tropubleshoot -> Resync).
Purge.
Save.
Re-enable auto-resync.
Re-open the file.

This should solve the problems, or at the very least pin-point more what is the problematic override.