[Zubersoft]

I think it would be best to get your tablets matching again (as far as the database). To do this, create a library backup file on the primary device under Settings->Backup and Restore->Backup Library, and restore that backup file on the second device. Then you should be able to sync and it should be back to working incredibly quickly. Normally MobileSheets should just look at the file hashes to detect when nothing has changed and skipped any data that is not necessary. Some sort of change has occurred between your devices where it sounds like this is not working as intended. Hopefully making the second device match the first with a backup file will get things back into a good state.

Mike