Folder Redirection - Wrong final path

About a month ago I've noticed the desktop folder redirection has stopped working as expected.

For example:

User 1's desktop folder should be redirected to \\fileserver\UserProfiles\LondonBranch\Desktop\User1

However, they're being redirected to \\fileserver\UserProfiles\BirminghamBranch\Desktop\User1

Here's an example of the event log:

Failed to perform redirection of folder Desktop. The folder is configured to
be redirected from \\fileserver\UserProfiles\BirminghamBranch\Desktop\User2> to \\fileserver\UserProfiles\BirminghamBranch\Desktop\User1>

The following error occurred: Access is denied.

Obviously access is denied because that's the wrong folder, but take note that the group policy is configured like so:

Folder redirected for group BirminghamBranch to \\fileserver\UserProfiles\BirminghamBranch\Desktop\%USERNAME%
Folder redirected for group LondonBranch to \\fileserver\UserProfiles\LondonBranch\Desktop\%USERNAME%

I've enabled advanced logging of the folder redirection and I can also see this in the event log:

Username change detected for redirected folder Desktop. The username used for redirection was user2. The current user is user1.

Just something else to note, it doesn't look like the group policy is actually being updated from the DC's but I cant confirm this at the moment.