So yesterday in the middle of a wedding ceremony I got my newest K3II on a tripod in the back with the 55-300mm HD, IS off, single shot, manual mode, iso 200, 1/60th, F5.6, normal AF, etc. and everything has been fine so far in that string of photos and I push the shutter and I hear what sounds like a tennis racket coming unstrung and the image is totally blurred. Hit it again, same thing. I wouldn't have been surprised if I had taken the lens off and had the mirror fly out, that's what it sounded like! Switched out immediately to my 2nd camera and finished the ceremony. Then when I had a chance afterwards, switched lenses (I probably turned it off and on too, I did not remove the battery) on the problem body and everything was normal again, and has been since for about 100 images more.
I'm guessing the SR wigged out and moved the sensor violently during those 2 exposures for some reason. It was around the 600 image mark for that camera and it has taken about 100 images since with no issues. I have been using the camera for a week and it's still within the return window.
I'm thinking it was a momentary software glitch and not a portend of a major camera issue... but I was also wondering if anyone had any other opinions.