ASK 21 WinchX Launch Bouncing

[Avio]

When using WinchX on ASK 21 the glider would immediately launch into air than hit back to ground and just bounce up and down along runway and not lift off. Any idea what could be the cause?

 

Air towing is okay.

 

Tried it on the Discus and it works normally.

 

However, the Discus model now could not switch on the C4. Battery already on and GPS showed up okay. The C4 was previously okay. What could be the issue?

 

Avio