So I'm finally following up my original post just for the sake of closing it out. I had set the amp aside myself because I got frustrated with the resetting and nothing seemed to work. I've reflashed the firmware more times than I can count - I even bought a new SD card - someone on another post was able to clone the contents of an SD from a working Amplifi 75 using the 2.60 firmware, and shared the image, so I put that on a new SD card and swapped it out. At first, it seemed to work, I wasn't getting the lockups that the amp had sprialed into from the resetting, but it quickly degraded again. I have found all kinds of posts about there being issues with the motherboards being flaky, the bluetooth itself being shoddy, and one guy knew a dude good with electronics repair and he found a faulty capacitor or connector and replaced it.
I've tried everything in every post. I've went into recovery mode and flashed different versions of the firmware. I've factory reset it over and over and over and over. I've tried different power cords, different outlets. I've used the Bluetooth, not used the Bluetooth. I've left the back panel unscrewed thinking that it was a heat issue. The amp just exists in a cycle of resetting now.
All I know is that at this point, the amp is useless. It worked really well for me for about a year and handful of months, but then it just completely fell apart. It was given to me by a friend because I didn't have anything, and I really wanted to make it work, but I think the money that it would cost to either send back to Yamaha/Line6 or even find someone local to repair it I could spend on a new amp that would work 10 times better (and longer). It's out of warranty, and the bothersome thing is that as far back as I can in the life of this amp, for some reason, Line6 has been less than helpful to the community of musicians who gave them money for these amps. The only replies I've seen and heard of (particularly when they were still making it and it was under warranty for most people) were "Do a factory reset. Get another USB cord. Oh well, you'll have to send it to us at your cost and pay us to fix it."
I think at this point...I'm just done with it. I'm out 5 bucks for the SD card, so it's not a loss money wise - but it's just frustrating that the Amplifi series has in the end proven to be an overhyped, shoddily built product from Line 6.