Under Dinette 12v Shows Only 11.6V

[KJRitchie]

My 12v socket under the dinette is used to plug in USB adapters to power phones etc. However, I notice the voltage on the wire feeds only shows 11.6v. When I plug in my DC power meter it shows even lower voltage but when I plug this meter in the TV and bedroom wall sockets it reports 12.9/13.0v (trailer is on shore power).

I requested electrical schematics from Airstream for my trailer model and received them but can't determine where the 12v leads for the under dinette 12v socket route. I figure the issue maybe a bad connection somewhere.

I removed the subwoofer about a year ago but the wires are now inside the wall behind a riveted plate under the mouse fur. I wonder if the 12v supply is also part of the 12v circuit for under dinette 12v plate. If I remember correctly the 12v feed for the subwoofer was a plug, not butt connected wires.

Anyone have experience troubleshooting such a problem?

Thanks

Kelvin