Weird enchanting table bug..? Button shows up with no enchantment and cannot be clicked on.

I'm not sure what's going on here, but I've created various custom enchantments that can only be applied to this "custom item" (it's a retextured command block with an enchantability component). Occasionally, when putting this item in the enchanting table, it shows a button that doesnt have an enchantment in it, and clicking on it does nothing. At this point you are forced to add bookshelves and hope you get lucky or enchant something else to re roll it. Is there something I'm doing wrong/any way to fix this?