death wobble a truly terrifying affair so I sympathise, mine also had a knock coming up through the steering on bumps
Fixed mine after following a similar routine to yours except I done the work myself.
Did the preload on the top swivel pin - critical to get that preload correct assuming that your LR chap did that right when he put in new swivels
Next Wheel bearings, with the wheel off the road shouldnt feel any side/side nor top to bottom play to confirm both these are spot on
Next I checked all four steering ball joints for wear. even the slightest is not going to help
Then I replaced the front axle bushes, all of them. I initially put red polybush in but they were harsh, replaced with blue
Then I replaced the front dampers both fronts passed the bump test but when on the bench neither extended to full length by themselves!! Both fucked and replaced. Made a huge difference to handling but still the brown trouser wobble still occured sometimes
Steering box was ok, I did try adjust some of the play out of it, be very careful you dont over do it as you will crush bearings inside the box which will need a stripdown to replace. I ended up getting a recon steering box which improved the steering feel no end. as did the new intermediate steering shaft in the engine bay
Lastly on on the basis of the fucked front shockers I removed the newish steering damper, a blue part, it extended and compressed nicely but all the bushes were shagged!!!. I bought a branded item and found it to put up a heck of a lot more resistance than the "blue" part.
Fitting this and ensuring that the bushes were crushed tight.
Death wobble totally fixed!! Just because the damper is new don't mean that it is fixed.
the clonk through the steering was a lot better also. I found that the front ARB links were dead and with these replaced the car has beenb perfect since.
Any or all of the above fixes can contribute to death wobble
Shitroen C4 GP 2007 1.6HDi - Wife's daily written off, farewell trusty but slightly unpredictable steed
Pug 307 - son's daily runner Sold to Arthur Foxhake
Range Rover Vogue 1993 - my daily runner
Daewoo Matiz 2002 - Sold
Jaguar x308 Sovereign 4 litre - nicked by Fathathestag might be up 4sayle soon
Triumph Staaag 1973 - cheaper than a mistress.. just
Range Rover 1972 - ongoing extensive restoration
Range Rover 1972 - complete shed but in line for restoration
Land Rover 1969 SIIa SWB - belongs to Fathathestag but maintained and welded by me
BMW E46 318i touring - sold to hhhugues