"Assertion failed: Error querying default thread scheduling params: 3"

Hey,

for whatever reason, I'm receiving this error on one specific project of mine, as soon as I open it. Googling the error doesn't help me, so I'm asking you guys now - maybe (hopefully) someone knows an answer on how to solve this.

I'm running Unity 2017.3.1f1 on a MacBook running the newest Mojave. I haven't tried my other Mac yet since I'm on-the-go and not at home.

All my other projects run without a problem. The project that causes this error, ran perfectly fine the last time I worked on it from this MacBook (two-ish weeks ago). Now, whenever I try to run the project, Unity completely freezes and has to be force-closed.

There's one more error before that, which tells me

 NullReferenceException: Object reference not set to an instance of an object
 GameModel..cctor () (at Assets/Scripts/GameModel.cs:1984)
 Rethrow as TypeInitializationException: An exception was thrown by the type initializer for GameModel

GameModel is my class to store and load a bunch of levels and configs. Line 1984 does not make any sense at all, and there's no error there either.

Thanks for your time!