Okay, so the error 500 should be fixed on latest and I just commited another fix so that the actual error appears in logs in case there’s another bug in there.
If you get an error 502 then the moving takes too long and times out. I made lots of changes over the last couple of months to move more metadata when moving posts. I tried to optimized it, but it highly depends on the amount of data and might still be too resource intensive for some server to do all the work in under 30 seconds.
The solution will be to refactor this one more time and store information about moved posts permanently in the database (instead of a temp table) and do all the heavy lifting in a background job.