Thanks JD -
All along I kept thinking that it WAS working - so it should go right back together - but that's not true at all.
One of the bars had broken the stud/bearing assembly at one bar end (probably BECAUSE the wheels aren't aligned) so I've never actually seen all four bars mounted.
I was only assuming it had been working (previous owner said it was - but you know how that goes).
Plus one bar, still mounted, was very bent - so there's no way that could have fit if everything was right (again,probably bent BECAUSE of the star wheels being off).
I'll loosen one end as you suggest and try again.
WAS going to try that originally but the nuts and bolts are really nasty looking. Just didn't have the energy for that fight last night.
I'll hit it again today.