Multiple Panelview 5/04 DH+ problems

So I've connected 3 existing 5/04's over DH+. Each PLC has a local Panelview with DF1 to the RS232 port. After a few hours, one Panelview will start communicating and writing to registers in one of the other PLC's!! Anyone ever seen something like this? How do I make it stop? I have DF1/DH+ passthru disabled on all 3 5/04's.

To be clear your Panelviews are connected to the PLC's serial port?

Check for messages instructions using the DH+ network that reads or writes between PLC's. Or the SLC's are using "Global Status Words" to communicate across the DH+ network.

I agree that MSG instructions are more likely to be the root cause of the problem. Code doesn't just change after a few hours.

Check to be sure there is no logic modifying the DH+/DF1 passthrough enable bits.

Check the PanelView terminal programs to see what the DF1 destination node numbers are. Really, they should all be Node 1 talking to Node 0, because DF1 point to point ignores destination node numbers.

I don't see a way for an SLC-5/04 to turn on passthrough and invent a target address that's not in the packet.

But then, this morning a man came out of the woods next to my house carrying a ukulele case and wearing a rubber ape mask. So nothing really surprises me anymore.