Thanks for reading everybody,
I did look at all the other posts, and nobody had the same byte error as I did and none of the advice on those seemed to work. The only one I haven't tried yet is removing the Atmega and bootloading to it, but I'm not sure why that would make a difference, I'd appreciate some direction!
avrdude: verification error, first mismatch at byte 0x0000
0xff != 0x0c
avrdude: verification error; content mismatch
avrdude: verification error; content mismatch
Arduino Uno, on a Windows 10, Arduino IDE 1.8.2
I was using the Adafruit Motor Shield 2.3 with a couple of servos and stepper motor, and a 12V power plugged in. I'm wondering if I shorted it at all.
As an aside, I put the same setup on a second Arduino and had no issues or errors, so I'm not sure what I did wrong the first time...
Thanks again!