Hi Robin
My experience with the so-called “Altitude Lock” is that it acts more like a clutch and not a lock, so no matter how hard you tighten it, you can still cause the altitude to change by using the altitude adjuster.
I also find there is a little backlash in the Azimuth adjustment knobs, although I have got used to this and can predict the behaviour as I get closer to Sigma Octans, overshooting much less frequently now.
Cheers
Dennis