I've observed a bug where the navball bounces around the top or the bottom of it when coming near to it. Because I'm bad in describing I added a video (Links to the timestamp are in the video description; the video is unlisted so that only people reading this issue can find it, if you want I'd remove it after you've seen):

https://www.youtube.com/watch?v=joZYF9XZu-A

If you need logs or any other things to investigate this issue please tell me.

I think it maybe could be a problem with Kopernicus, which replaces the standard Kerbol System and maybe if you use some static data in Telemachus, this may cause the problem because the data is incorrect for this system. But I'm not sure, it's only an idea of what could be the reason...