Yup, we had SQLITE in the same fashion (synchrnous=OFF, and other non-safe settings, no WAL also) and had occasional crashes, then someone had to manually delet

Yup, we had SQLITE in the same fashion (synchrnous=OFF, and other non-safe settings, no WAL also) and had occasional crashes, then someone had to manually delete the database (in our case it's for a desktop app, a tool, so no server-like requirements, yet we want it to be stable). Would remove the MDB_NOSYNC then, and see how it goes...