I used to play older versions of Kerbal Space Program and I had this problem which is really annoying.
I place a probe with relay antennas around a planet or moon so that it can bounce signals for other vessels as they lose direct sight of Kerbin. Then when I'm done I focus on other things and run other interplanetary errands. Years later I go check my setup with the relay probe and... it's left the parent body.
I always make sure that the relays' orbits don't have them come anywhere close to moons (usually they just hang right over Jool's atmosphere). In fact sometimes I have them orbiting Laythe, for example. Yet when I go checking on these years later, I have relays orbiting Kerbol and not wherever it is that I had parked them.
I had thought this to be a known bug but I can't find anything about it. And I'm playing 1.11 now, build 3066, and this keeps happening. I just had a relay on Eve lost its orbit.
I'm feeling stupid now. Am I doing something wrong?