Can not join Dedicated Server with JUST this core mod loaded, stuck on loading 99%

[mindforger]

server log does not show anything suspicious https://pastebin.com/A7XJA71x

but the game log is strange https://pastebin.com/S0xwQaMv

PS: i cleared the cache, deleted the acf file and cleared the downloads/content folder mutiple times

2021-02-19 09:34:16.564|Main Thread> Error: Caught exception in MyNetworkReader: VRage.Network.MyRpcMismatchException: Message_RpcMismatch
at VRage.Network.MyTypeTable.Serialize(BitStream stream)
at VRage.Network.MyReplicationClient.ProcessServerData(MyPacket packet)
at Sandbox.Engine.Multiplayer.MyTransportLayer.ProcessMessage(Byte[] data, Int32 dataSize, UInt64 sender, TimeSpan timestamp, TimeSpan receivedTimestamp)
at Sandbox.Engine.Multiplayer.MyTransportLayer.HandleMessage(Byte[] data, Int32 dataSize, UInt64 sender, TimeSpan timestamp, TimeSpan receivedTime)
at Sandbox.Engine.Networking.MyReceiveQueue.ProcessMessages(NetworkMessageDelegate handler, TimeSpan delay)
at Sandbox.Engine.Networking.MyReceiveQueue.Process(NetworkMessageDelegate handler, TimeSpan delay)
at Sandbox.Engine.Networking.MyNetworkReader.Process(TimeSpan lag)

i am quite far away from understanding the serialization part but from a glance and how it behaves and because it only is an issue when connecting to a dedicated server ... is there a chance your deserializer can not handle an empty server?!