Lock barrel issues

Hi all, about a month ago I had some scrote try to rob my landy; https://www.landyzone.co.uk/land-rover/attempted-theft-now-need-new-door-handle.377616/#post-5324198

After a bit of going round the houses figuring out if I'd ordered the wrong replacement, an angle grinder on the spring button housing got the new one to fit nice and flush. Fiddly pain in the arse...

New problem now though. Same locks as before, but the new one is incredibly stiff (have lubed it up) if the screw is tightened, to the point where unlocking it feels like it might snap the key / sometimes it doesn't properly unlock. Problem is, if I slack the retaining bolt any then it works itself loose after a few key turns and the screw drops out.

Any advice? Have I somehow messed up the installation of the lock into the handle? Can't figure out how to stop it blinking well happening.

Cheers in advance!

You may have offset the new if the original one got damaged.
What model of defender do you have.
Sounds like it wrongly set. But could be knackered from the supplier. Was it working okay before you fitting in the door.

Cheers for the reply saxa. I've got an N reg 90, so 1996 300 tdi.

Yes it was working fine before the change of handle. In terms of it all fitting internally, it's all correctly aligned as far as I can tell. Seems to me, if the bolt is screwed too tight it is a pain to turn the key, but if I slack the retaining bolt off the bolt then moves when the arm set within the door moves left or right as the key turns and works its way free. I don't think it's anything to do with the lock itself, just the bolt, plastic washer, and the arm that connects to the locking mechism control rod.

Debating swapping the new arm, bolt, plastic washer assembly for the old one as they should all be swappable I think but massive faff disconnecting the clips and con rod etc to the locking mechanism