The 8-pin connector in Bob Y's last image was the culprit. Although the connector was fully seated and latched, there seemed to be some play in it and lightly touching the wires/connectors would make some of the pins disconnect from the socket in the HIC module.
https://www.youtube.com/watch?v=09ZESkYkpEM
This is particularly alarming because this 8-pin connector is a "jesus bolt". If it is disconnected, or in this case, loose, there is the potential for both fuel pumps to turn off. I've contacted support this morning because I think this might be a safety/design issue.
I'm not sure why it is loose -- could be the plug, socket, pins, or maybe some tension/stress from the wires pulling on the plug, etc.
I've also looked at a few past flights in the Garmin Logbook and charted the Fuel PSI on some randomly picked flights. Apparently this issue has been occurring intermittently since at least Oshkosh 2021. The indication is that the fuel psi would drop about 2 psi instantly and return some minutes later.. which I wouldn't notice in flight. (ie. 46 psi vs 44 psi)
The plan is to replace the ES-60009 HIC module with a ES-60009-1 HIC module (apparently it has a skirt to prevent things from getting underneath the pcb). I'm going to extend the wires with 12&14ga tefzel, solder sleeves -- enough to help avoid the abrupt bend in the wires. Put a new molex connector on and use the TPA (
Terminal Position assurance) inserts which help prevent the pins from moving around inside the connector. Depending on how secure/flopping around the wires are, I may secure them further with an adel clamp somewhere.