Hi

So this happens either when a player spawns in, or randomly whilst already loaded in. For spawning in, I was able to get the following error from the client debug log. 

AddUI: Unknown Parent for "MagicPanel_MagicFpsPanel_Text": MagicPanel_MagicFpsPanel
UnityEngine.Logger:Log(LogType, Object)
UnityEngine.Debug:LogWarning(Object)
CommunityEntity:AddUI(RPCMessage)
CommunityEntity:OnRpcMessage(BasePlayer, UInt32, Message)
BaseEntity:CL_RPCMessage(UInt32, UInt64, Message)
Client:OnRPCMessage(Message)
Client:OnNetworkMessage(Message)
Facepunch.Network.Raknet.Client:HandleMessage()
Facepunch.Network.Raknet.Client:Cycle()
Client:Update()​

This can be ignored as it doesn't cause any issues for the client.