Sophos Central Wireless v2.3.4-3 - change mesh frequency band - button grayed out

Sophos Central Wireless v2.3.4-3

Hello, I have the following problem:

Due to the fact that the mesh is relatively unstable and the access points regularly lose connection, I want to change the mesh frequency band from 5 GHz to 2.4 GHz.

When I edit the mesh SSID, I can change the frequency band, but I cannot save the settings. The button is grayed out.

Do I really need to delete the SSID and create it again? The effort to reconnect all APs to the LAN to apply the new config would be enormous.

Thanks for your help.