The DTTG database on iPad and iPhone show differently with that on Mac. Some tags become groups and some files appear on the root folder. I try to verify thoroughly and nothing changed. I thought the files are just some extra files but actually not. When I delete the files, the files in the right places on Mac will disappear.
A screenshot of the Mac would be great too, thanks. In addition, were any issues logged on any device (see e.g. Window > Log on the Mac)? Are you able to verify the database (not the sync store) on the Mac successfully?
According to the log the remote sync store was verified, local databases can be verified via the File menu. In addition, smart groups are not supported by DEVONthink To Go yet and therefore hidden by default.