Got the big bike out this week after not riding it much over the winter, and the rear wheel is sort of siezed. Very reluctant to spin forward or back in the bike.
Fearing some free-hub problems, I removed it and cleaned all the pawls – everything looks fine, bearings seem OK, basically the freehub is working nae bother. Put it back in the bike and it’s the same problem – something is binding when the (12 mm) axle is tightened up. Any ideas on what that might be?

Maybe the hub end caps? Basic question, but is the hub meant to rotate independently of them once they’re clamped up on the bike? So the wheel should spin completely freely off the bike if you hold it by the end caps?

Yep. Should spin freely while holding the end caps.

Mine did this after a 2 month lay up whilst I abused my hardtail over the wettest part of winter, it’s an X12 axle on mine.
It was the 2 bearings in the hub body that were knackered, felt very gritty and lots of drag. I replaced them with some SKF bearings from a bearing factor, If you need the sizes I’ll drag the receipt out and let you know.

could be the washer between freehub body and drive side bearing?

Thks for the suggestions – I thought I’d sorted it by cleaning the thru-axel and putting a light-film of grease on it. Wheel now spins freely.
I wonder, though, if this has just not enabled the hub axle to spin round the thru-axle, and that the main bearings are seized?
The wheel should move around the bearing, with the hub axle stationary, right?

could be the washer between freehub body and drive side bearing?

It’s this. It’s always this. Stupid design, really.

Look on the floor for a round spacer the same diameter as the axle, about 2mm deep.