I've been dealing with this bizarre issue on my Garmin Oregon 450 GPS, and I need help diagnosing and fixing them. For some reason, I can't catch a break with these undocumented unsolved mysteries. Here's the situation:

(Original)Stuck in USB Mode:

When I turned on the GPS, it shows the USB icon as if it's plugged into a computer for file transfer, even though it isn't. If I plug in a USB, it works for file transfer. The issue disappears when I cover the pins from the back case (with the USB port) to the main board with electrical tape. When I do this, the device works perfectly fine, but I need a more permanent solution without relying on tape(outside, if I want to load maps I will need to disassemble my gps). This issue was sort of fixed by resoldering the CMOS battery(which garmin says is not needed -

Power Button Problem:

After I desoldered and potentially re-soldered the CMOS battery, the GPS starts when I press the power button, but it doesn't boot fully. It powers on but does not complete the boot process. The thing with the CMOS battery is, I don't know if CMOS is the right term. The battery's voltage is lower than a standard cmos bat, at a shocking 0.24V. This causes me to think it's either completely cooked or it's a specialized battery. Either way, garmin's user manual(link) says it is not needed. See page 36, saying "Data Storage Life: Indefinite; no memory battery required"

Steps I've Taken:

I've desoldered and attempted to re-solder the CMOS battery (model 10N4). I've tried electrical tape on the USB pins, which temporarily solves the ghost USB issue completely even if I press the power button. I've put a little bit of isopropyl alcohol down the USB port(device was off, port was disconnected), it's still drying as I type. I have NOT disassembled any further than the secondary back plate with the battery slots. If someone thinks that will help, I will try to.

Can anyone contribute to this discussion? I have found radio silence online. Thank you very much.

Photos:

Thank you for reading this, and for any ideas you may have.