Update - after many hours testing I have isolated the issue to the TCA quadrant. I have mapped the engine switches on the quadrant to enable CJ4 engine starts like on the A320. Worked fine till SU3. Engines still start but with the switch ON the alt increments in 1000 and with it off increments in 100… I can’t help thinking it’s related to a comment in the SU£ patch notes about changing one event to set from toggle as that appears related…