Disco 2 Wobble

Have a Discovery 2 that has steering wobble at 50mph after hitting a bump. I have checked ball joints etc and had the wheels balanced but cannot seem to find anything. Checking the forums brings up to check preload but that appears to be for Disco 1. I've checked the panhard rod and there's no play. I did remove the steering damper but it had some resistance but I wasn't sure how much there should be?
Thanks

Preload is as you say for D1 (the famous swivels).

Have you tried swapping the wheels front to back?

Also check steering column UJ's for play and replace the steering damper if you have any doubts, cheap enough.

The lower steering column does have a click but no play. Does anyone know how much resistance a damper should have?