KAS winch gets ripped off

[Sharpy]

I made a tiny rover with a drill (smallest rover wheels), deployable over a cargo ramp. I tried pulling it back in using a KAS winch, but the winch keeps getting ripped off its attachment point. I tried to make it more sturdy - 6 struts around the winch to the wall - and the effect was the same. Brakes released, the rover is really minimal, a kerbal can push the rover around, there are no obstacles (runway), everything seems to be just right to let the winch pull the tiny thing. I press 'Retract" and the next thing I see is the winch lying on the bottom of the cargo bay.

Why? How can I fix it? What am I doing wrong?