SU6 mixture issue
Not sure if this is the right place to report, but after SU6, when I selected the built-in 'Set Best Mixture' function, the mixture lever moved all the way back (killing the engine) and remained in that position, the animation twitching constantly.
After that I was unable to manually move the lever to get it out of that state, either by dragging or using shortcut keys.
I've never used that function myself (didn't even know it existed), but there is a complaint about the same issue on Avsim. I suggest you file a zendesk request.