Yes, I remember that one Roy. Luckily, this one is the other one!! But to Big Duke's post. He's hit the nail right on the head. It's all about accurate and exact fitting too - and understanding the interrelated mechanical complexities. I'll give you an example...... Are you sitting comfortably, then I'll begin. Early last year, someone had a Mk2 scope fixed by someone and it was still mechanically crXp. Then another amateur enthusiast had a go and so on and on. The deflection was tight or just wouldn't operate at all once it was locked up. So, fixer number one had filed away the brass internals to loosen it up a bit. Fixer number 2 had done something that affected the range mode too and had made it totally unuseable to boot. Both, simply because they didn't understand the two axis principle.
If it was assembled loosely, it all operated mechanically. But at tightening-up time it became screwing up time - literally! Nobody had told them to read the EMER or in thge absence of the EMER or experience, just use a bit of what my mum used to call Common bloody Sense! Or what I call, the bleedin' obvious. The front shade was putting too much load on the inner sleeve which was loading up the...... Anyway it's all inter-related and the fix was easy. Or it WOULD have been but filing away the meal meant a small job became a much longer rebuild plus machining operation. Not yours Roy! Assemble loose, tighten down and test as you go.