Electrical Oddities - Help!

[Bella Sera]

Problem: Turned the battery switch to off, the cabin lights stayed on. Tried other AC breakers and their systems worked with the battery switch off as well. Thought "This can't be good". As an electrical idiot, thought I would see if anyone has a good starting place or simple solution.

My system is a Marinetics AC/DC CB panel, standard off/1/2/both battery switch mounted on the panel, house bank and starter battery, and a Link 2000 Inverter/charger.
In troubleshooting, here is what I have discovered so far: (1) With shore power disconnected, everything works as advertised....ie none of the boats systems can be powered on until both the battery switch is turned on and their CB is flipped on. (2) When shore power is connected, the Link 2000 comes on immediately (doesn't matter which position the AC "Shore power" CB is in)....but even though it shows"Charge", it doesn't reflect any amps passing until the battery switch is turned to 1, 2, or both....then appears to work fine. (3) With shore power connected and the battery switch in the off position, I can turn systems on just by flipping their DC breaker switch.....but they seem to be undervoltage (ie cabin lights are dimmer than normal) and I hear a faint hum (assuming this is coming from the charger in the cockpit locker). If I flip the battery switch on, the hum goes away, as does the apparent undervoltage.

So is this a miswired Link? Bad battery switch? Gremlins? Am I running a risk operating the system as it is? I've had the boat just over a year and didn't notice this issue throughout last sailing season......but was rarely onboard while plugged in. Think the Link was installed about 5 years ago.

Suggestions welcome. Thanks,