I don't have the solution, but to relay a weird experience with the same...
I imported an object from 3D warehouse and got similar results.
I copied the object into a second PLN file and the image map mysteriously
corrected itself. I haven't tried to replicate the process.
What happens if you convert the object to a morph?
Marc Corney, Architect
Red Canoe Architecture, P. A.
Mac OS 10.15.7 (Catalina)
Processor: 3.6 GHz 8-Core Intel Core i9
Memory: 48 GB 2667 MHz DDR4
Graphics: Radeon Pro 580X 8GB
ArchiCAD 25 (5010 USA Full)