I experienced a sloppy linkage on one side of the servo arm , thus not allowing the aileron to fully extend / contract were the other did
This was causing a roll back / out when turning hard left , gentle turns & strait flite there was no issues it was always when pulling hard G's
A hard pull into a loop was to say the least.......very interesting @ 180 mph
With a new tight servo arm fitted and the issue was gone , so my conclusion was at high speed small play will affect plane stability