Debugging c++ code isn't an easy task except you are a professional programmer and familar with debugging tools like IDE Visual Studio.
I would recommed doing one of this ways:
Go back in what you have done in the past. F. ex. delete the items in your DB if you think it's an item problem. Or change back the code in your core if you modified it.
The other way: Set up an new fresh core and DB and try to add your changes step by step.
As you have an assertion error in MoveSpline.cpp you also can study the code there and think about in general if you have changed something with movement. Removing fatigue could be such a thing.