Been getting a lot of these lately.
I've tried reinstalling the plugin fresh, but still get them :
[Error] Failed to call hook 'API_GetFormattedMessage' on plugin 'BetterChat v5.1.0' (NullReferenceException: Object reference not set to an instance of an object)
at Oxide.Plugins.BetterChat+ChatGroup.GetUserGroups (Oxide.Core.Libraries.Covalence.IPlayer player) [0x00006] in <6cd389ec69c3465ba81071a349312dee>:0
at Oxide.Plugins.BetterChat+ChatGroup.GetUserPrimaryGroup (Oxide.Core.Libraries.Covalence.IPlayer player) [0x00000] in <6cd389ec69c3465ba81071a349312dee>:0
at Oxide.Plugins.BetterChat+ChatGroup.FormatMessage (Oxide.Core.Libraries.Covalence.IPlayer player, System.String message) [0x00006] in <6cd389ec69c3465ba81071a349312dee>:0
at Oxide.Plugins.BetterChat.API_GetFormattedMessage (Oxide.Core.Libraries.Covalence.IPlayer player, System.String message, System.Boolean console) [0x0001c] in <6cd389ec69c3465ba81071a349312dee>:0
at Oxide.Plugins.BetterChat.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x003af] in <6cd389ec69c3465ba81071a349312dee>:0
at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <9affce1cd15c4ec183941adef8db1722>:0
at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <4452f821def6406d834e4149849fe7ea>:0
at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <4452f821def6406d834e4149849fe7ea>:0