Thanks for your advice. I have removed the ring, but the screwdrive & locking peg still do not move forwards.

I've now contacted a Pentax repair firm who quote a minimum of £85 + VAT + carriage. Much cheaper than buying a new one or refurb I suppose & if 20,000 clicks is relatively low, then presumably worth doing as I do like the camera.

I've been a long term Pentax enthusiast; an MX being my mainstay for 20 years of mainly railway photography. Apart from a clean, it never needed anything (& was second hand when I bought it!).
I changed to a K10D 3 years ago & it's been great. However, from recently the lens lock doesn't work, nor the apparently connected body screwdrive autofocus peg. Neither of them 'pop' out but remain in their respective holes.
The camera is nearing 20,000 shots, but I haven't changed the lens this number of times!
Has anyone experienced this or had such a fault repaired? Is it worth getting it fixed seeing the camera's done so many frames?