I'm posting this experience in case it can help.
Dropbox desktop app on a Macbook with 2 user accounts. Both mac user accounts signed in to the same dropbox account. Desktop app version 193.4.5594 and MacOS 13.6.4. Not using the File Provider version.
Symptoms: User 1 all is well. User 2 has high dropbox CPU usage even when "everything is up to date", and very slow to sync. Troubleshooting shows that User 1 Dropbox has Full Disk Access and User 2 does not. However, attempts to add Full Disk Access to Dropbox when signed in to User 2 do not work. Deleting access for User 1 and re-adding has no effect. Quitting Dropbox, Rebooting, do not work.
Solution: methodically reinstall Dropbox
Uninstalled Dropbox.
Deleted Dropbox Full Disk Access from the User 1 account (still present even though app is not installed). Deleted Dropbox from the Login Items on both accounts (still present even though app is not installed). Logged out User 2.
Reinstalled Dropbox from User 1. Added back Full Disk Access from User 1.
Logged back in to User 2 and now see that Full Disk Access is also enabled for User 2 (no action required to do this). Logged out User 2.
In User 1, signed in to Dropbox and let it finish indexing and verify CPU drop to nearly zero after about 5 minutes.
Log in to User 2, sign in to Dropbox. Took several attempts. Let it finish indexing and after about 10 minutes CPU has also dropped to nearly zero.
Re-add Dropbox to Login Items on both accounts.
Now all is good and Full Disk Access for both users survives a reboot. Nearly zero CPU for both users (after first few minutes).
So if you have this symptom and unable to add Full Disk Access, this process could help.
