Polymer-Version: v0.13.8+1.21.8

When I give myself a item via /give the data looks like this:

When I click on it in the creative inventory it changes the data to this:

Notice that the changed data is the same as the data you would get with /polymer client-item but on its on the server which it doesn't belong and so it also breaks functionality

Is it your own mod with item? If so show the code. This is usse on mod side very likely

I used filament to generate these items.
But it also happens with the items of the PolyChess Mod which don't use filament, thats why I think it's a problem with Polymer

Any logs in the console?

Unfortunately, no

Generally it seems to be some sort of mod incompatibility as it fails to modify the received creative packet