Try putting a one-second delay in the "Delay" field. What I discovered some time ago is that a big sensor camera (with large file sizes) doesn't have enough time to finish writing the file to drive before the next image is ready - because the exposure time for bias frames is so short. I add a one or two second delay always, for all types of frames for that reason.
that sounds exactly like the problem I’m hitting. I’m at kstars 3.5.8 and cannot see any later release, has it been fixed in a ‘bleeding edge/roll your own’ way and is not in an official packaged release yet?