v8.1.9
This morning an assembly line was powered down to replace some broken stuff, but comms to the other lines became almost non-existent until it was brought back up.
Did I read on some other thread that there was an update to the driver for such occasions, or was that just a fever-dream?
8.1.15 has this release note:
NJ, FINS, and DNP3: prevent the accumulation of Requests and long delays before execution while driver is not connected. This had impacts on memory usages and read/write timeouts from scripting.
Drivers aren't coupled in a way that would allow one being down to interfere with another, but you can certainly add coupling in your application by writing scripts that read or write from multiple devices in one execution. If you have any kind of heartbeat or other timer scripts or something like that this could be the problem.