Freewheel locks up when skewer is tightened?!

[Andy B]

Sounds like the axle spacer between the drive side hub body bearing and the freehub body could be missing or damaged.
Could be a damaged or dislodged pawl in the freehub mechanism.
Could also be to do with the seal between the freehub body and hub.
I've seen all these things cause the symptoms you describe on Novatec and other similar hubs before.

Difficult to determine without seeing the hub.

Sounds exactly like a missing/damaged/wrong/incorrect fitment of the spacer between the hub bearing and the freehub bearing

sometimes the spacer has a chamfered edge on one side and it will only work one way round