I've been trying to simplify the issue reported in RPR v2.0.32 Uber Shader - Material Assignment *for stickers* - transparency ignored on material assigned faces
I have come up with the following simple test file (attached) instead.
It demonstrates the issue much better than the linked Community Post Above.
It uses the Alpha channel of the image map file through a Mix Shader.
One input on the Mix shader controls the Decal Material.
The other input on the Mix shader is set to the same Material settings are the rest of the cube.
If the main material of the Cube is refracted in any way the Faces where the Decal material has been assigned will display by stripping away some of the rendering layers (or it changes the refraction... I'm not sure what goes wrong).
However on materials (such as the yellow cube) where the material is not transparent the decal is able to mix in without error.
This should clear up the many versions and test files which were made for the previous post into the core issue, and hopefully make it easier to debug.