Y axis stalling

[richie00boy]

OK, before I take things apart a bit more and get lost, here is what I have found.

1. The motor knob becomes stiff when the leadnut under the gantry can be at almost any point along the length of the leadscrew, i.e. not just at the ends.
2. I have unscrewed the leadnut from the gantry and can see the leadnut housing bobbing about relative to the gantry again at almost any point along the length of the leadscrew.

I'm thinking that there could be two ways for bending the leadscrew. One if the leadnut was not mounted centrally, and the other if the chassis is out of square or the leadscrew not exactly in the middle of each end piece. How can I check for all of these? Because there is also the possibility that a bent leadscrew has been fitted at the factory - which I'm hoping is the case and my machine is fundamentally sound. Also I would not be that bothered if the leadnut was not mounted centrally because if I convert to ballscrews I would be fitting a new mount.