Thank you for the fast reply!
Of course i have installed the KER Mod. I think without it, it is a real challenge!
Ok, i see what you mean. I have tried it and i think it is a stable orbit. At least the orbital period and the orbital velocity are the same. So i hope that they will stay in that position.
Thank you very much for this workaround! But i would be very happy to solve the problem or to know how to avoid this bug...
btw: With an electrical engine lowered to 0,5% of thrust it is really easy to get an orbit which is to the exact meter identical to another vehicles orbit. With 4 relay satellites in a 2,500.00 km orbit, it was a 1h work. Nothing difficult or impossible (if this annoying bug doesn't appear).