I'lll have to assume that the lens hasn't been damaged in the mount area, and has always functioned in the same manner with the K10. If it used to work well, and now doesn't, then it sounds like it either has worn, or has been damaged to the point where it is no longer within spec.
If it's always been this way, I would guess that you're experiencing one of those rare situations where there's a "perfect" mismatch in you lens and camera mounts. This happens, for example, when a max (+) tolerance part is mated with a max (-) tolerance part, so you get the worst fit possible with parts that are still within factory specs. To the other extreme, I had a friend with a stone stock 1960 Chevy that ran like a Pro Stocker with a blue-printed engine -- just one of those freaks of the manufacturing process.
If the lens is still under warranty, I'd send it in to try to get them to either replace the whole thing or replace the mount. Mention that you have a number of lenses that work correctly with two different bodies, and though this lens works correctly with one, the mount is too loose with the other. Another potential scenario is that they replace the pins with some that are a hair longer, but if there's any visble wobble in the lens to camera mount, I'd consider this contact pin fix unacceptable for a lens under warranty.
If it's not under warranty, and you have a good lens tech in the area, it would be worth getting an estimate to either replace or modify the lens mount. Speaking as an old motocycle mechanic who had to somehow resurrect some very old, obsolete bikes into something approaching road-worthy condition, I would imagine that the mount cams could be either peened or cross-hatched to tighten the body to lens fit.
If none of this is feasible, then I'd probably sell the lens, realizing that if the new owner experiences the same problem, that you'll have to (without any hassle) refund the money and take the lens back and try again. Most likely you won't have to, but realize that this could happen.