The flaps and airbrake will work perfectly fine with force / application in a LINEAR ORIENTATION WITH THE SIDE RAIL. If someone else (like a CFI) reaches from the side of the rig, it will apply a twisting / deflection side load on the mechanism it simply isn't designed for. The left side flight controls are designed for PILOT USE ONLY while sitting in the sim rig. It is a recoverable issue if the airbrakes are pulled out from adverse side loading - but it is totally avoidable if you just don't do it! So don't do it ...