The "bad inline model number #" error is most frequently caused by either an outdated demo (unlikely) or trying to run a demo on a map version that the demo wasn't intended for (i.e. an updated map file that has the same filename as a previous map file). In-game, it's caused by a static texture (decal) being placed on a dynamic entity (brush).

Which map was this demo recorded on?

I have the same problem with a snakewater demo, tho i am unable to find a download of a legacy version of the map. The demo was recorded on 21.03.2016 and a week after i could not load the file anymore, i couldnt find anything in the patchnotes on teamfortress.com aswell

I've never had this before but already got 3 errors like this while clip sorting for March submissions for the Top10 and I'm not even halfway done. Even one on Gullywash which is an official map so isn't that a bit weird? Verifying TF2 and restarting Steam doesn't help.

Update: 4 out of 22 submissions got this error. Now I don't have enough worthy clips to fill the Top10. Fixing this will probably help get enough clips, hmm. I don't know the map for most of them though.

Luke you probably wont be able to fix them, its an issue related to a mm patch that was released back then and almost all the demos recorded prior to it got corrupted.

Hmm that sucks, thanks anyway. Time to scout for more quality clips then.