Or if you want to commiserate with other people with the same affliction:
This problem seems to affect some people and not others. One person added more RAM and the problem went away. Another user switched to hardware encoding and it worked. Yet another user found that a specific filter was causing the error.
I hope we figure this out one day.
If you want to invest some time to try to help narrow the problem:
Make a COPY of a project that fails
Systematically remove one item at a time (a filter or transition) - each time export after one single subtraction and save the project file with a new name
If the export succeeds after a subtraction, try to re-add the item - does it still fail? Post the before/after to this post so we can examine what might have been the problem.