I don’t have an immediate answer. Could you perhaps export the extension and share it? I’ll could then try it in a test game to see if I get the same issue.
As a heads up, whatever you’re doing in the “slot empty extension”, you’re using a number larger than the maximum number supported in Javascript. Regardless of whatever else is going on, tt will not function as you have it in the screenshot with that as an animation name or number.
I believe the max safe number is 9,007,199,254,740,991 but what you have is equivalent to about 10 magnitudes higher than that.
I think I found the problem. I am using the “Item” behavior on an object NAMED “Item”, So I think it bugged up in the system, because it works with non-“Item” named objects.
Non-custom behaviors seem to work just fine on global objects, so I will test to see if other custom behaviors do the same with global objects like my normal custom behavior does.