Factorytalk ME HMI Question Marks all over

I have a PanelView 6+ that runs a ME program. Recently, I've had a couple occasions where the HMI graphics has question marks all over the screens. And restarting the panel/system seems to clear that issue up. Any idea of what could be causing this?

Sounds like the HMI is losing connection to the PLC. Indicators which display values read from PLC tags will instead display question marks when failing to read the value. Things like multistate indicators will have a set indication for a failure to read as well, by default showing 'Error'.

The question marks means that the PV cannot get the data from the PLC. This would mean either there is an error in the tag name or expression, or a loss of communications.

Since it does not always show the question marks we can probably rule out an error in the expression/tag. It is most likely a loss of communications. I would begin by inspecting the connections either at the PV, the PLC, or the switches.

OG

Had the same issue a few months back. Suggested multiple possible issues and corresponding solutions. Boss's answer was to install a toggle switch to cycle power to the HMI. (On restart, the HMI tries to establish comms.) It worked ... keeping the line going until the place shut down.