This has happened on more than one occasion.
My QSI 583 WSG will hang during a flats session and I have to disconnect and restart SGP.
The exposure times were set by the flats wizard for each profile.
All in all it is a great feature, but it seems to hang the camera every so often.
This is the only time the camera hangs up when using SGP , all other operations very successful.
Logfile link for your perusal. Errors, of course, are at the end.