Can't import unwrapped model in RC

I have the issues:
I created a new plane over the exported model of my Scan export form Reality capture. I want to do something like the demo you guys did with the tree-bark and make it a textured material and not an object anymore. My object is 64K and is 4x16 Textures. I can do what you showed in your video, but when I try to import the same way but with 4xUVW Maps I get an error.
What and how could I solve this?

Erro message with a 64K UVW Map
“texture coordinates of a triangle are indexed to different textures”