Been thinking a bit more about why sensor was only working intermitantly.
Not a problem with water getting into connection block as was like new.
Heat from exhuast didn't seem to be the issue as heat shield still in place.
Circuit board inside also looks as new
Only thing was that there was a fair bit of black gearbox
up in top of unit. Perhaps over the years probably gets a bit stickier and doesn't all run back down into gearbox and builds up and affects sensor
If someone has same simptoms may be possible to flush out
by taking off unit from car, turning it up side down and pouring in some white spirits, spinning around shaft by hand or with a drill and draining off fluid that should have thinned out
Anyone done this or fancy giving it a try?
Here is picture of inside unit