not often i get to comment on the general section.
before anyone says thank christ, i`ll say it for you.
i had a mk1 superstar for ages, fitted with 3-9by40 tasco silver antler. it was attached by low single mount. never a problem.
i now have a mk2 with 3-9by50. attached with two piece high mounts. lots of problems. the bsa dampa system doesnt like it.
it might be worth a few quid to get a one peice mount and see if it makes a difference.
since i went two peice i have to check it every time i go out. the one piece stayed true all the time.
just a thought though, if you have iron sights use them now and then. this makes you hold the rifle in a fashion you will take up. irons won`t allow you to cant, as wont diopters.