Sir_Paperbag

Went in-game to test your idea, and it seems you were right! I could swear I never touched Alt, though... Thanks a lot!

Tried to make a short mission, one stage to get out of atmo and a second one for the rest of the mission. Easy. But as soon as my vessel approached orbital velocity, it started rotating in a random direction for no good reason. Here is a video where you can clearly see that the vessel starts rotating from a standstill without any SAS input/torque applied.