Hi David,
thank you for your reply. I will upload a substantial portion of the model (the full model consists of +500 files), it will take a little while to sort it out.
On my side, the problem is persistent, but not consistent - meaning that it appears all the time but might affect different objects or materials. It is somehow related to the GPU, because it used to work fine with my prior GPU (AMD FirePro W9100) with rare exclusions that I reported here in the past but could not be fully resolved.
From my personal experience, once a file is affected, you can’t get rid of the problem anymore. In this particular case, it started when I added the texture for the tower and did the UV mapping. Once assigned, the more or less plain white weathered material starts behaving odd.
Best greetings and thanks!
Will put together the demo and upload it on support.
Cyana