We already copy to an interim temp file on shutdown--just try to open it before overwriting old backup file
Still wish there was a way to detect corruption while Zotero was still open and pretending to write to the DB, but I don't know of one (other than making a copy of the DB and trying to open it, but as far as I can tell we can't release the file handle on it to then delete it or check again later)...will keep working on it.