FYI - this was problem in TS2 as well. The solution then, as now, is to save often and also save using "Save As". Something about using "Save As" seems to ward off many of the problems. What I do is Save As (i.e.) New Town A, then New Town AB, then New Town ABC, etc., depending on how long I play. When I'm finished playing, I delete the older saves, rename the newest save to "New Town" and then hang on to 1 or 2 of the most recent previous saves, just in case the last save is corrupt. It is a bit of a juggle with the deleting and renaming but I've been running into enough bad saves (without CC but do have some Mods) to make it worth it.