I'm having issues as well. I get close to two hours of imaging at Unity in the ZWO ASCOM driver and then SGP crashes. Yes, even .15.
On top of that the FLATS wizard fails to work properly. It takes 3 frames, gets down to the 4th at .48 seconds and then fails to download any image at all.
If I try to manually take a flat frame with anything under 1 second...it fails to download. I'm using the .5 driver with SGP .15.