My K-x was one of the unfortunate few that suffered from double-image blur at shutter speeds between 1/80th and 1/160th of a second. I posted a thread about it here (
https://www.pentaxforums.com/forums/pentax-dslr-discussion/96746-k-x-shake-ca...technique.html) after I'd had the camera for a few months. In the end it went back to CRK for repair, and they "dismantled unit to S/F new gyro circuit assembly".
I then went to SE Asia for 5 months and lo and behold, the problem reoccurred. So when I got back home I sent the camera (along with photos showing the issue) back to CRK, who very gracefully agreed to repair it even though it was a week or two out of warranty.
This time they "dismantled unit to S/F new main PC board and gyro circuit assembly". I've taken around 100 shots at the shutter speeds that used to show the problem with the same lens I used to use and so far every shot has been nice and sharp, with no blur. I've also taken a couple of hundred other shots (confirming that my new Sigma 17-70 2.8-4.5 is back focusing - when will it end?) of which plenty have been at the relevant shutter speeds, and everything's looked good.
So I guess either it was the gyro assembly that was the culprit (and I was unlucky enough to get two bad ones in a row) or the main PC board. Unfortunately now the camera's speaker doesn't work so I get no focus confirmation beep or sound in movies. But I can live with that.
Edwin