Eyepieces vary greatly in how much rotational force is required to turn them. A tablet with an offset camera will naturally induce a torque to the eyepiece. If this torque is more than the frictional resistance of the eyepiece it can turn. Fortunately camera software automatically rotates the image regardless of portrait or landscape mode. To avoid this problem simply use the tablet adapter at either minimum or maximum zoom settings only then position the tablet so its self weight is acting against the zoom stop.