After putting up with its slipping height adjustment for months, I finally cracked and got rid of it, now sitting an a much better but quite different feeling mesh style office chair
the old one has served me well for 7 years now...but the slips were ever 10 mins now and thats annoying when you're already screaming at the screen about to pound on another hapless keyboard when something that should work doesn't..
I seems there is a bug in some of the Raspberry Pi's OpenGL extensions...meaning that some of the things I want to do can't be done, quite the same way...took quite some research to work it out, and find some possible work around.. I'm not there yet.
So I'm going to blame the new chair.