GP300 expanded mode oddity

[Norman]

Hi. I have a 465-495 MHz GP300 (P94YPC20D3AA) -- a factory eight-channel model which I expanded to 16 channels. Though RSS correctly shows my desired 16 frequencies, I noticed that whatever I program into mode 8 is also received in the channel 1 position. In other words, I have no channel 1. Mode 8's signal is received on both 8 and 1.

Except for this odd behavior, the other 15 modes are working perfectly. I don't understand why mode 1 insists on behaving like a copy of mode 8. Whatever I program into mode 8 also outputs to mode 1 -- as if position 1 and 8 were somehow "strapped". In case it matters, I have mode 16 set to scan the other 15 modes -- but I don't think that matters.

Has anyone else experienced this with an eight-channel GP300 expanded to 16-channels?

These radios are easy enough to program so I can't imagine that anyone would hard-wire channel 1 to channel 8 at the switch. Anything's possible but I thought I'd ask here first before tearing apart the radio to inspect the channel selector.

I've programmed dozens of expanded 4, 6, and 8-channel GP300s and P110s and have never seen this before. Aside from the obvious -- like triple-checking my programming, I'm puzzled by this and would appreciate any advice.

Thanks in advance!

[Will]

Bad channel selector switch. The switch is Binary...