@SebHillaire, great work on the new Sky Atmosphere features in 4.25. Been playing around with it the past day or two.
Unfortunately, I can confirm I have the same issue as @Stiian in 4.25. The “pivot point” (as it were) of where the Sky Atmosphere renders seems get more and more distorted translations as the player rotates around the atmosphere and rebases. To clarify, the scene component is always in the right place, it is the render side of the atmosphere that is off, which seems very odd to me. I would assume the hsf code just uses a transform, and the underlying engine properly puts that transform in the right place after rebasing.
Oddly enough, it only seems to happen when possessing a pawn. When I eject and fly around the scene, there does not seem to be any issues. I believe this is due to rebasing not taking place when ejected, but I’m not sure.
I understand the “planetary view” of the Sky Atmosphere is probably not a high priority, but if you can find a fix it’d definitely be appreciated. I know I’d like to integrate it before 4.26 comes out, however far out that may be 
I’m going to try and go through the code myself later tonight and see what’s going on. If I find anything I’ll post it here.