[https://github.com/Leviathan-Studio/CraftStudioAPI/blob/7d3689cf4097bce1c1571372e82d848bf0ce0821/src/main/java/com/leviathanstudio/craftstudio/client/animation/ClientAnimationHandler.java#L175](url) this line is causing a ConcurrentModificationException since you can not just remove an object while iterating it.