I discovered today that if you upgrade a network containing a single MS220-8p that was on MS 15.21.1, that then became MS 15.21.1/CS 15.21.1 with the firmware split, the ghost CS entry gets left at 15.21.1 with no way to upgrade or remove it... 🤔
As you would expect the only options for the network upgrades are the MS tree.
If my answer solves your problem please click Accept as Solution so others can benefit from it.