Does the issue occur in the editor or during gameplay?
During Gameplay.
If it's a gameplay issue, please specify which movement system and camera type you're using (free movement vs. grid movement, third-person vs. first-person) or N/A if not applicable:
Real-time, Grid-based, 3rd person, but I believe it's N/A.
Briefly describe the issue you're experiencing:
Game breaks down if you try to save after changing player's model.
Are there any errors in the in-game debug console or external console window?

Provide the steps necessary to reproduce the issue:
- Change player's model via script or via map settings;
- Save the game via script or manually - the game will break down.