Yes, an unsettled IS system will indeed cause blurring, ghosting, double-imaging, etc. I don't know if Pentax has in-camera IS or lens IS, and the characteristic blur from the Pentax may differ from what I get with my Canon IS lenses. I am also not sure exactly how long it might take a Pentax IS to "settle", however on my worst Canon IS lens, it takes less than a second. I know that sometimes a fraction of a second does matter, however as a general rule when using stabilized gear the rule of thumb is to shoot early and shoot often. You might notice sports photographers with the great white lenses usually shoot a couple seconds before any anticipated action actually occurs, partially to allow for IS settling.

I've learned a trick recently myself that helps with IS settling. I've started using back-button focus, wherein I've decoupled AF activate from my shutter button and configured a button near my right hand thumb as the button to activate AF. I normally use AI servo, but the same button works with single-shot AF as well. On a Canon, activating any one of AF, Metering, FEL, or shutter all initiate IS. By having independent control over AF, I also have independent control over IS, and I can usually keep IS activated if I anticipate the need to shoot, so by the time I actually do activate the shutter everything has already settled. I'm not sure if the Pentax supports reconfiguration of button functions, but if it does, you might try to separate AF control from shutter control, and give yourself a bit finer grained control over it all.