I've encountered this problem before and after the most recent patch. While building satellites, the RV-105 RCS blocks seem to impart phantom forces on the craft. Might be due to hitbox clipping even though the visual models are not?
Here is a picture of the satellite I'm building. RCS at the top. (I moved them during troubleshooting to no effect.) Struts added during troubleshooting as well.
And here is a link to an unlisted YouTube video showcasing the problem:
Taking the RCS block off stops the problem from occurring.
Thanks!
Specs:
OS: Windows 10 (10.0.19044) 64bit
CPU: Intel(R) Core(TM) i7-7700K CPU @ 4.20GHz (8)
RAM: 32631
GPU: NVIDIA GeForce RTX 2080 Ti (11049MB)
SM: 50 (Direct3D 11.0 [level 11.1])