How to reproduce:
1. Get your craft to Gilly's orbit (probably any small body would work).
2. Turn off the engines, RCS and SAS.
3. Initiate craft rotation and stop giving user input. Without SAS the craft will continue to spin.
4. Now look at your orbit and watch in disbilief how it changes with your craft's orientation.
The effect is so pronounced that I can escape Gilly's SOI by simply rotating the craft. Yeah, nice orbital physics simulation, guys...