No idea. I have never encountered this in my game, perhaps because CERTAIN PEOPLE refuse to send me an afflicted file.
Currently uploading an error13 infected save to kludgemush. Should be there in about 10mins.
Upon trying to make the next save after this, I received error 13. However, the thing with error 12/13 and the "18 minute" saves, is that while they may happen after playing a while, restarting the game allows saves to return to normal. I can pretty much guarantee that Ill get a save issue after ive made changes in game, such as using CAS or editing colours of multiple items in build mode. Though it also shows up after extended play. This happens in the base game without mods and is inflicted upon people randomly (while some get it, others do not), so I doubt there is anything that can be done about it until EA fix their save routine.