I was orbiting a planet with my 3 escorts when suddenly the log window started filling up with these messages:

Report from Helm:
Right sideslip is ENGAGED

Report from Helm:
Right sideslip is DISGAGED

Report from Helm:
Right sideslip is ENGAGED

etc.... repeatedly

This loop carried on. Some notes following:
- The keys on keyboard were not pressed
- I had just beamed up all my team
- No enemy ships in orbit and no combat beforehand in the system
- I had never used the sideslip command this game (or even once...)
- After waiting a bit, I tried to carefully press keys but could not do anything (e.g. couldn't move bottom menu, Ctrl-T etc)

EDIT: After leaving to grab a coffee, the looping stopped. but I think I lost around 1-1.2 mission time.