Hi everyone!
I usually don't post in the forum much, but I've run into a problem that's driving me a bit crazy. Now I'm not new to KSP I've been a player since I bought .13 way back when. However I can't for the life of me figure out this Duna interplanetary transfer vehicle I'm trying to design keeps rotating in orbit when I throttle up the engine. As you can see below it's docked to a "mock-up" lander similar to the one I plan on using. Through testing I've found that if I undock, the vehicle flies just fine, but while it's docked it rotates. The SAS isn't keeping it stable, and I've checked to make sure I hadn't accidentally set a trim in my game. I even tried it with multiple engines (was testing to see what would be the best to use for the flight to Duna) and they have the same result. I have noticed that if I shut the SAS of it takes more time for the ship to start rotating oddly enough.
I'm really at a loss as to what's wrong with the design, and any help would be greatly appreciated.