Unpivot node confusing column selection

Hey everyone, first of all a big thanks to you guys, my introduction to knime and the forum has been amazing.

I’ve stumbled upon something that confuses me a bit, so hopefully you can help me out (again).

My issue is with an unpivot node that is configured via flow variables, which has worked great so far, but in this specific instance the unpivot configuration claims that the columns are missing, even though i can see in that very same dialogue that they’re not:

What could be the issue here for the unpivot node claiming the columns are missing?