My GameMode class is modified as well and derived from blueprints. At first, I only overwrote beginplay. I recently have overwritten a few other functions. In my project, the map and everything loads fine. As soon as I open any blueprint, the game crashes.Mine does the exact same thing and throws a serialize error anytime I open a blueprint. Downgrading back to 4.7.6, I can immediately open any blueprint that was crashing on 4.8.
Edit: The other odd thing is that I only recently implemented my custom game mode (derived my class from it). My crashes were occurring before it was called. Was there anything you changed that allows your game to work correctly on 4.8?