Any money guesses that it's to do with demo management. Anytime I complete a room and exit it, a demo isn't saved, and trying to view demos for that specific room will show a demo from an entirely different hold. In my case, I was playing one of my homemade levels, but when I went to play a demo for it, it was showing a room in the tutorial.
The following lines are consistently appearing in my drod.err file:
Assertion error in line 348 of .\Db.cpp: "demoIndex.find(demoID) == demoIndex.end()"
Assertion error in line 349 of .\Db.cpp: "demosHoldIndex.find(demoID) == demosHoldIndex.end()"
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--That guy with a million different aliases since he doesn't like this name anymore.