BUT - I just did two things and could save a lot of times without any crash and quit D:OS normally. Unfortunately I didn't try to save between step #1 and step #2, so I suggest if you want to try this out to begin with step #2.
#1 I deleted all saves except 1 and the two quick saves. I now have only 3 saving slots in the one profile I made.
#2 I enabled V-Sync and Triple Buffering (which was activated automatically after I clicked on V-Sync).
So far it seems to work. On the first attempt it stuttered a bit, but saved successfully. I then quick saved 7 times in a row without crash.