I've been trying to mod multiple entities (in this case mobs) into the game. After initially having quite a bit of trouble with the new syntax (last time I wrote a Forge mod was in 1.8) I started to look into existing mods in order to figure things out.
I actually managed to get a single entity to work properly with some mostly copy-pasted code, but after adding a second one, upon trying to summon it, the EntityRenderManager crashed the game with the crash report description that is in the title.
I since rewrote a lot of code because after searching through a bunch of forums it turned out the code I had earlier had a bunch of depreciated stuff in it, but now after the rewrite I still get the same crash but now with both entites (a.k.a. none of them work now).
The full crash report is as follows: https://pastebin.com/0eRdCCxM
Main Class: https://pastebin.com/6E8nVpqP
Rendering Registries: https://pastebin.com/jn2yx69c
Entity Registries and Attribute Init: https://pastebin.com/zyrtsLeb
Renderer Classes (both are pretty much the same): https://pastebin.com/7wgdSbJN