The game currently automatically changes to Control Mode 2 for vehicles so that's where you should check the mapping of all controllers, including mouse. In the Map Controllers menu choose one controller at a time, in the menu below choose Mode 2 and scroll down the mappings list. X and Y axii are the ones rotating the turret. Notice that you'd also have to calibrate the axii you want to use, otherwise the turret will keep moving. Mine kept turning towards the sky until I calibrated the Y axis. In a plane I hadn't noticed anything strange! Hope you'll find the culprit.
