[keos]

Anyone experience an issue where the shutter (or mirror, can't tell which, I just hear the slapping) continues to actuate for several shots even though it's in one shot mode? I noticed it the other day using a 50-135mm with a dying SDM drive. I took a shot then I hear a whole bunch more actuations like it's been possessed by the gremlins of the SDM.

[reduno]

There were a few reports of mirror flap on the K-3 II early on, especially with aftermarket batteries that were nearly depleted:
K3II Mirror Flap - PentaxForums.com
k3ii "mirror flap" when battery is low - PentaxForums.com
However, I don't believe this a common issue with the K-3 II but I would suggest you make sure the firmware is the latest version.

[jatrax]

Has happened occasionally. More common with the K-5 series. Most seem to be linked to either a low battery situation or third party batteries that could not provide enough voltage under stress. Possibly your failing SDM was pulling more than normal with a low battery.

In general it is not something to worry about unless it starts to occur on a regular basis. Some people have experienced it once and never again. I have. It is really scary I'll admit but if it only happens the once they I would not worry. I think I have had it maybe twice on my K-3II over 5 years.

[aaacb]

As reduno posted above, and it's also called sometimes "shutter flutter". I think I like "SDM gremlins" more

I had a k3ii, and I've experienced it once in 4 years and 35k shutter actuations, took care to keep the (oem) batteries charged and never happened again

[Ishpuini]

I seem to remember it happening with my K-5 indeed. It was still under warranty, so it got replaced/fixed (don't remember which) by Pentax.

If you can avoid it by keeping a closer eye on your battery with a spare at hand, that's probably best, as having a K-3 II repaired could become quite expensive. I asked a quote for a repair of my out-of-warranty K-3 II that had gotten soaked on the inside. At that time the K-3 II was still being sold (the last ones in stock in Europe). The service center replied with a cost estimate of around the same amount as the last new ones in store were being sold for, i.e. around 800 EUR!! Needless to say I didn't have it repaired (it still worked and still works BTW), but bought a new one as back-up instead.

[house]

Has happened a few times with my K-3II. Over years of usage it's happened maybe five times. Usually I provoke it with pixelshift in compbination with frantic menu use.