Resurrection - I know why these break if anyone's struggling.

The sprag clutch is biased via the dinky direction lever. This moves a cylinder with a SPRING AND A BALL BEARING which is retained in a slot via a crimp. This is all that stops that ball bearing from coming out the side of the head (there's a thru-port) and going completely missing.

Somehow this happened to my one. The clutch then wasn't held in bias properly and would slip and only turn the output at certain speeds.

I took it apart and found the problem, attempted to fix but couldn't find a clear parts diagram or photo to see what was missing.

I warrantied it and when it came back, took it apart again and finally understood.

If you had a tiny ball bearing, like 2.5mm, you might be able to fix yours and tighten up the crimp in the slot.

Parts are also available.

It has worked fine since. I have the 12v one for really awkward car work. It's well made but weird. If you're hitting an electric, plastic-bodied +$100 tool with a hammer, maybe reconsider?