Too new here to report a bug, but I think this might be one (check out the weird ‘matrix’ text in the bottom corner of the panel)
Panel settings:
I’m using Unity 5.2.1f1
Use the Unity Bug Reporter located in Unity Editor → Toolbar → “Help” option → Report a bug.
It looks like the renderer is using dirty frame buffers.
Try to use 5.2.1p4. In Patch 3, they fixed the issue regarding the renderer displaying garbled stuffs.
We are having the same thing happen.
Its a known bug we have fixed. It happens with images that have no source image. We used to assign a default white texture when no image was assigned but this created issues when using your own custom shader so we changed it and this bug crept in where the texture from an other material would be used. We have a fix now, it may be out in the current patch if not It should be out soon but for now just assign a white texture instead of empty slot.