As per title, players get kicked or sometimes crash. Server has just been wiped. I have tired restarting the server and also disabling the mini-copter added seats plugin as well as spawning in a fresh mini-copter without any seats. 

This error code is put out in the rcon:

(23:46:23) | 67.166.238.85:53347/76561197963753162/[God] Veptaa disconnecting: FormatException: Input string was not in a correct format.System.Number.StringToNumber (System.String str, System.Globalization.NumberStyles options, System.Number+NumberBuffer& number, System.Globalization.NumberFormatInfo info, System.Boolean parseDecimal) (at <00000000000000000000000000000000>:0)System.Number.ParseUInt32 (System.String value, System.Globalization.NumberStyles options, System.Globalization.NumberFormatInfo numfmt) (at <00000000000000000000000000000000>:0)CommunityEntity.CreateComponents (UnityEngine.GameObject go, JSON.Object obj) (at <00000000000000000000000000000000>:0)CommunityEntity.AddUI (BaseEntity+RPCMessage msg) (at <00000000000000000000000000000000>:0)CommunityEntity.OnRpcMessage (BasePlayer player, System.UInt32 rpc, Network.Message msg) (at <00000000000000000000000000000000>:0)BaseEntity.CL_RPCMessage (System.UInt32 nameID, System.UInt64 sourceConnection, Network.Message message) (at <00000000000000000000000000000000>:0)Client.OnRPCMessage (Network.Message packet) (at <00000000000000000000000000000000>:0)Client.OnNetworkMessage (Network.Message packet) (at <00000000000000000000000000000000>:0)Facepunch.Network.Raknet.Client.HandleMessage () (at <00000000000000000000000000000000>:0)Facepunch.Network.Raknet.Client.Cycle () (at <00000000000000000000000000000000>:0)Client.Update () (at <00000000000000000000000000000000>:0)UnityEngine.Debug:LogException(Exception)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()Version: 44795​

try deleting the steamappps folder of your server and re run the Rust update, then re update oxide/umod and see if this persists...
Could also try validating your client game files as well...

The error is coming from a plugin that provides custom UI.