The sensors connected to Simnet can’t be found.

Sorry to here that GMI 10 didn’t worked as supposed seems to me that manufacturers put tings on the internet as if they existed long before thy reach the market. I have been looking at the GMI 10 for myself for a while to get a digital display that can lock analogue:) I have a Garmin MFD that works perfectly with NMEA2K.

Yes the devices can detect when they are failing and disconnect themselves but if the fault is in the devices connection to the bus within the device (physical layer) this won’t help since it is the connection part that’s failing. For instance the node baud rate set incorrectly affects other nodes when it attempts to go online or some other short circuit problem inside the devices signal wiring. All devices talk on the same two physical lines so there will be interference as if to people speak at the same time.
/Lars