I will tell a scary story here.
Soon after I had bought an HS125 700 crews reported sluggish performance and roll control. 3 or 4 times the engineers reported "nil defect found".
On a heavy crew sector I was down the back of the aircraft and woke up in the morning to look out of the window and saw the right aileron fully up. I looked at the other aileron and that was fully up too! To cut a long story short the servo tab had been rigged wrong together with very slack aileron cables (wrong cable size tensioner units used) caused both ailerons to upfloat in flight, completely to the mechanical stops. All aileron control input was doing was lowering one aileron. No wonder it was a bit sluggish. On the ground all returned to normal and "no fault found". When I reported this to the engineers they did not believe me. As sort of inadvertant wing bending relief?