Tiltrotor elevons not working



I am using MindPX in combination with a tilt-rotor (Convergence) and Firmware 1.8. The vehicle does not respond to any control inputs from the RC for pitch and roll (elevons do not move) when in altitude and position mode in FW configuration (the elevons respond to changed in attitude, though - also yaw through differential thrust responds to RC input). The problem goes away in stabilized mode. Has anybody encountered this and knows a quick fix? Have tried everything (and had a few bad landings).