Auth error on one device in chain

Description of the issue:
One Windows PC in my sync chain has stopped syncing.

Steps to Reproduce (add as many as necessary): 1. 2. 3.
Leave chain - does nothing.
Use sync internals to disable sync - OK.
Restart brave - OK.
Start syncing - OK.
Insert passcode - OK.
No sync - Error.
Internals disaplys ‘auth error - connection failed’

Reproduces how often:

Brave Version(See the About Brave page in the main menu):

Type of devices currently running on the Sync chain in question:
1 x W7 PC
1 x W10 PC
1 x Android phone
1 x iOS phone

Additional Information:
Sync was working fine until recently.

Brave is now 1.21.77 with no change.

No input on this from anyone?