I have been using SSC quite a bit today.
Error #1: All was going swimmingly for about 10 minutes, until the screenshot disappeared and I was left with a couple of objects on a light blue background.
When I tried to "Undo", I got the error message:
I shut down SSC and restarted it, and had to redo my work (lost approx. 10 mins of work), so it took me about 10 mins to redo the work, doing Ctrl+S every now and then.
That's 20 mins in total so far.
Then I had a break, and put in about another 10 mins of additional work, doing Ctrl+S every now and then.
Error #2: Then the same error occurred, with the same outcome.
That's 30 mins work lost. The air was blue with curses and I was frightening my son and daughter.
I restarted SSC, and found that one arrow and one squashed-up box were all that was left, and were in the top left hand corner of the screenshot I had been working on. I had not put them there.
I moved them and started to redo all the work, doing Ctrl+S every now and then.
Had a break and drafted this error report.
...then, same type of error:
Image file destroyed/overwritten.
So I started incrementally saving a copy of the image file at every step, and each time SSC failed, I went back to the last saved image file and started from there.
Finally got there.