Unable to join the server while simple UI plugin is active

Error I receive:
disconnecting: RPC Error: addui

what triggers the error is this line:
CommunityEntity.ServerInstance.ClientRPCEx(Network.SendInfo(player.basePlayer.net.connection), None, “AddUI”, Facepunch.ObjectList(broadcast.Replace("[TEXT]", self.flagText)))

Can we get some update did the methods for building UI changed?