Joining 2 objects in Blender 2.8 loses UV mapping on 1 I'm a bit new at Blender, so this question might sound stupid, but I've tried every suggestion I can find here and nothing is working for this.

I have 2 separate objects with their own UV and material. I've named the materials and the UVs to be unique prior to joining them. I've made certain that both objects have both materials. But, as soon as I join them, both objects always try to use the same UV map. I've tried added vertex groups and assigning them prior and after joining, but that was no assistance, either.  Is there some basic step I am missing?







Blender file:
https://1drv.ms/u/s!At__F5mV_pKlgdFMYC3Ivy50t0VZZQ
If more UV maps are linked to an object, the materials used by that object need to have an Input > UV Map node attached to the Vector socket of their textures, specifying which UV Map to use, so either of these: