Sourcebans uses KeyValues to make admin configs, which are not case sensitive and randomly get casing wrong update after update. (Will root keyvalues with "group" instead of "Group" sometimes).
Sourcemod's admin-flatfile uses SMC parsing, which is case sensitive and only recognizes "Group".
https://forums.alliedmods.net/showthread.php?t=265684
https://forums.alliedmods.net/showthread.php?t=265635&page=8
Could go back to several past updates where the same thing has happened time and time again.