You should have a plan for network instability or outages that causes a safety stop for anything affected by that fault domain. If uptime is important then you

You should have a plan for network instability or outages that causes a safety stop for anything affected by that fault domain. If uptime is important then you might have two separate networks side-by-side. You can also split a large fault domain into a few smaller networks. There is also the possibility of being clever with how things are wired so that the PHY can be physically cut out of the bus by a watchdog, but that doesn't help with cable faults and introduces its own possibility for failures. It's also possible to have another set of emergency stop signal wires side by side with the digital communications in case there's an issue.