Right, I know everyone's views on Lammy speedos being like windscreen wipers

but after replacing complete speedo, inner / outer, drive, drive bush etc. Speedo packed up after 5.7 miles

Now I'd checked that the speedo worked with a battery drill in reverse on the end of the inner and the speedo had a lovely steady needle action, and did so when tested on the road for the aformentioned miles. It was the second SR nylon worm drive I had fitted as the previous one showed wear in the centre. I know I can get a full metal set from MB (at a price

) but has anyone tried these and had any success or a mix of the metal and nylon? I'm starting to think that the worm drive and pinion bit are meshing but not quite enough, hence the speedo packing up after such a short time and at speed. Is there any way of checking how well they are meshing? Am thinking that the short spacer may need filing a touch so they mesh better.
Any thoughts? And No, I do not want to go down the SIP speedo route or any other make
