My Mk2's knob started slipping as soon as it warmed up a little... the FAQ says 'contact support for a new one', but I got my baby off of ebay and the original receipt shows that it's over a year old (and yet never used, apparently), so I had to come up with a fix of my own: A corner of a handy plastic bag... I just tore off the corner, put the resulting very thin piece of plastic on the shaft, and pushed the knob on... it did the trick, no more slippage. I'd imagine that a piece of plastic sandwich wrap would do as well, if for some reason you can't lay your hands on a scrap plastic bag... anyway, just thought I'd share...

--pj