Need help with M4 - focus trouble with Screw Mount Lens

[nobbylon]

Nobbylon, my understanding is that if the 1M adjustment is correct, it stays correct and only the infinity adjustment (setting in cam follower roller) can drift. I have also always thought that the vertical alignment should be done before the horizontal.

Yep that's my understanding too. That's why you check the infinity first which gives you a reference point and then fine tune the 1 and 10 metre with the pivot cam and if necessary alternating between the two in minute adjustments. My experience and I don't have the correct jig for adjustment, is set the infinity and then check 1 metre on a tripod against a fixed chart. I've only ever seen it off by no more than 5cm and a quick tweak is all that's required. If the arm has never been taken off or the pivot screw messed with then yes just adjust the roller eccentric screw in the centre.
The vertical adjustment is a sliding mech in the vertical plane and as far as I can tell, it doesn't matter if you do it before or after. Doing it before probably makes it easier to see whether your horizontal(infinity) adjustment is accurat or not. I suggested the infinity first because thats the main problem, that's all.
The main reason I've had to adjust them is because of removal of the rangefinder itself. This has been to get access to, and remove the slow speed mech' for cleaning and relube.