using forge 35.1.36 (in 1.16.4), while customizing with fancy menu the mod detects the 2 entity spots as buttons, but they're invisible and can't be interacted with (no sound when clicked), with the second newest version it works, fancy meny doesn't detect the spots as buttons (as far as I remember).

You probably still have the old config file (mobs.json in the config/menucompanions directory) from v1.0.2. Delete that so it can be regenerated and report back if it works.

I updated to the latest version and deleted the old config, same problem, I also didn't notice any difference between the old configs and the new ones.

Fixed in v1.2.