Devices duplicated after adding them to the Sync chain

[Brave-Matt]

Description

Seeing users report that their devices are being duplicated on the Sync chain after being added. This is present across all platforms (Desktop, iOS and Android). Once a device is added to the chain, duplicate entries for that device appear in Settings --> Managed Synced devices:

Further, as illustrated above, they seem to continue duplicating over time. One user encountering this also included some additional details:

Cannot test it now. But when I noticed the issue a few days ago, I had a lot of copies from my Windows Brave too… So it looks like an issue with the Desktop Version, that keeps creating new devices without noticing them. Until now, I did not see any mobile devices duplicating.

If you delete the duplicates on iPhone or iPad that do not share the same device id as the is shown in the MacOS Brave (but keep the one, that is shown in MacOS Brave), the sync stops working completely. Seems like the Desktop browsers are not only creating new devices that are invisible to themself, but they are also syncing new bookmarks using the new device ids.

This behavior occurs consistently, even if the Sync chain is completely deleted and start fresh.

Steps to reproduce

1. Start a Sync chain
2. Add other devices to it
3. Observe devices suplicating

Actual result

Duplicate devices appear on Sync chain

Expected result

Device should only appear once in list after added to the chain

Reproduces how often

Easily reproduced

Brave version (brave://version info)

v1.68.128

Channel information

• [X] release (stable)
• [ ] beta
• [ ] nightly

Reproducibility

• [ ] with Brave Shields disabled
• [ ] with Brave Rewards disabled
• [ ] in the latest version of Chrome

Miscellaneous information

User thread: https://community.brave.com/t/device-is-listed-as-multiple-different-devices/557152/10

Additionally, I can see this occur on my end as well — although they do not continue to duplicate for me, I do see the same device added multiple times, despite only ever having been Synced once: