[DiapDealer]

I can assure you that no other reports of Sigil consistently not responding (with regard images or any other repeatable scenario) are currently pending. You're of course free to use any program you like. If, on the other hand, you'd like to figure out what is special about your setup/process, we'll be happy to help track down the problem. Your call.

There is not now (nor likely to ever be) an auto-save feature in Sigil.

As mentioned here and other places, Sigil's scratch areas are not to be trifled with. There's nothing there for a user to make use of. There is only danger.