I noticed that your coremod couldn't patch in the "applyHotbarOffset()" method.
This is a raw copy of the log:
[controllable-transformer.js] Patching IngameGui...
[controllable-transformer.js] Failed to find method: net.minecraft/client/gui/IngameGui#renderSelectedItem()V

And it seems that it didn't work on ForgeIngameGui either.

Can you tell me the Forge version, Minecraft version and Mod version you are using?

This is fixed in newer versions!