Version: ALL versions

I could tell you that you are a very careless person. You have so many methods are not guaranteed to be thread-safe. An example is your ClientProxy, whose run() will run on FMLClientSetupEvent, this is a parallel event and called from a ForkJoinPool thread pool to your mod event bus. So you can NOT call methods such as in BlockColors, ItemColors, ItemModelProperties directly, because their internal HashMap is not thread safe.

Your code is like this:
Example

public void run() {
  ItemModelsProperties.registerProperty(ModuleTool.INFINITY_LAUNCHER, new ResourceLocation(Reference.MOD_ID, "cooldown"), (stack, world, entity) -> {
              if (entity instanceof PlayerEntity) {
                  return ((PlayerEntity) entity).getCooldownTracker().hasCooldown(stack.getItem()) ? 1 : 2;
              }
              return 2;
          });
}

Therefore, players will randomly get ConcurrentModificationException.

The solution is very simple:
Pass the event (FMLClientSetupEvent) to run() method, and wrap all the code with event.enqueueWork(() -> { //run here );. I hope there will be no such issues in all your future projects.

Fixed in 75e0676