If you change the name of a tag in a snapshot sub-account, and then you push that updated tag name into customer sub-accounts, the tag name will be changed correctly within the settings. HOWEVER, the original tag is left remaining on the contacts, even though that tag does not actually exist in the account settings anymore.

What should happen is that when a tag name is changed by a snapshot update, the tag name change should also occur at the contact level. Any contacts that had the original tag should have that original tag name updated to the new tag name.

This needs to be fixed ASAP. It's a huge pain in the butt to try to fix manually, and it has likely already affected hundreds or even thousands of sub-accounts.

I've already submitted a ticket for this, and they recorded a video you can reference.