Good news: Syncing works fine for you. The remote out of sync items are “informational”, it’s what the local device thinks the remote device needs. If the remote device itself has no out-of-sync items, it is indeed in sync.
As to investigating the cause: You could query the /rest/db/file endpoint on .stfiles on the involved devices (see Other hosts all at "Syncing (95%, 0 B) and following posts for explanations). This gives information about global and local versions on each device (and discrepancies thereof).