happens on a few locos, only when the exterior model of the front loco is in shot https://drive.google.com/file/d/1DC4jDaeuZu1uqF9RHRt-VKVjv7pc0VPw/view?usp=sharing
That is usually caused by a faulty asset. Something in the scenario or with the train hasn't been installed correctly by the looks of it.
Not insinuating anything, this can happen with pirated DLC. Can also happen by copying a DRM-protected GeoPcDx to a location outside of its "home" assets\provider\product folder so the connection to its _.sbn file is lost and vertex coordinates can't be decrypted.
Although it's more technically any Geopcdx from another folder into a folder with DRM, even those that don't have DRM by default (say if you copied something from a kuju folder to a new route - it would have the same affect, and also vice versa (so DRM Geo into a non DRM folder ))
I have noticed this with a faulty reskin - in the cab you don't normally see it but go to exterior view and it causes the problem you are getting.