Has the ST5000 enclosure been opened for a visual examination?
The rear panel small Phillips screws may be removed so that the clam shell enclosure may be opened.
All those rear-panel connectors are transferred to the internal circuit board by sockets and pins.
There should be "large"
power FET devices that may be measured using a multimeter for defects.
Assuming all the logic / display is good, then the brains are working, so I would look to the output driver circuitry.
https://raymarine.app.box.com/s/nwf2...ile/3273047443