Screen Broken

I created a mod (my second). It is an entity mod based on an Iron Golem. The problem is when I load this mod and launch it, when the game loads the screen is frozen. Music plays, the buttons can be clicked, but the screen frozen on the load screen. When I maximize the screen, the screen goes black, but the game engine continues to run. Has this happened to anyone before? There must be something wrong with my mod. How do I debug it? BTW I am an adult professional software developer, not a child.