[kylekatarn77]

Partway into that level the game crashes and I get the attached message.

[attachment stolen by Russian hackers]

[niffiwan]

That's a warning rather than an error, and you can continue past it by clicking "No" (IIRC).  However, as a player you shouldn't have to worry about it as is presents an issue with the mods assets.. Instead, run the normal version of 3.7.4, don't run DEBUG unless you need to generate a logfile to paste on the forums.

[karajorma]

Or keep clicking through the warnings until you hit an actual error that is causing a crash when you play on release builds.