Same issue here. HA receives data from Ethernet Gateway for only a few minutes and then:
DEBUG (MainThread) [mysensors.gateway_tcp] Connection lost with <_SelectorSocketTransport closing fd=42 read=idle write=<idle, bufsize=0>>
I also have MYSController connected to the GW and it remains connected. There is an open issue as others are also having the same problem. Am wondering if anyone here is having success with Ethernet Gateway connected to HA.
@Multimax do you send initial states for all children for this multi relay node? HA won't show anything that hasn't sent initial data to show.