No power to the disc drive? Everything else fine? Unique issue. X1

So here's an interesting problem I'm having with my Xbox one...

I had the infamous disc drive problem where it made grinding noises and had issues reading discs. I managed to deal with that, but then last weekend it wasn't reading anything nor was it making any noises. I decided to take the box apart and work on it.

After disassembling everything, I found that one of the gears on the drive simply wasn't budging, preventing the drive from spinning the discs. I was messing with this a bit and it was working great - until the drive simply stopped having power?

I was thinking that maybe the drive died, so I bought a new one (and do the logic board replacement). However, before doing anything with the new drive, I simply plugged it in to check, and again no power. So this had me thinking there was an issue with the motherboard.

I used my multi-reader (the best that I could understand it anyway) to read the prongs for the power connector on the mobo for the disc drive and I did get readings... which made me think it wasn't totally dead or anything. I then decided to get one of my xbox 360s out since they use the same type of power connection for the drives. I plugged the drive into the 360 and boom - power to it. I tried this with both xbox one drives and both get power. I then tried powering the drive with the 360 while running the sata (data) cable into the xbox one. While the drive ran and was reading the disc, the xbox one wasn't picking anything up. Confused...

Also of note, when the drive is connected completely to the xbox one, it does notice if there is a disc in it or not. No it doesn't run at all, but if you push eject on the One with no disc in, it makes the proper sound. If I force a disc into the drive just halfway even (no power means it doesnt feed it automatically) and then I push the eject button, it then makes the proper eject sound. It knows if there's a disc in it or not?

I'm not sure what else to try at the moment. Maybe something shorted. Problem is I don't know what to look for. Everything else works fine - the wifi, hard drive, controller. So it's a bit strange that it only affected the connections or something to the connections for the disc drive? Anyone have any ideas? I figured if it was a big short or whatever, like the south/north bridge chip, there would be more problems then just the disc drive. I'm not quite sure what to look for at this point, or what to even try using the multi-reader on. But I'm not ready to give up either.

Sorry this is quite long... it's a very unique problem don't you think? Any help/thoughts/ideas would be very appreciated!