I just ran into this as well, the link showed "blue" in the "Provision -> Fabric Sites" overview. When we looked in the "Tools -> Topology" section the links showed "red" and could be removed there.

You should check the plug & play section (Menu -> Provision -> Plug & Play). In my case the switch with this serial number was already registered there and after removing it from PnP the 169200 seconds backoff timer was gone after erasing the switch ...