I have a 2560 that I've been working with for a while (over a year for sure), programming it with an avrisp mk2. No issue this whole time, then suddenly, a couple of days ago it starts failing with
avrdude: verification error, first mismatch at byte 0x0002 0x01 != 0x95 avrdude: verification error; content mismatch
And very obviously not flashing (there's logic that blinks the LED on boot, and the LED isn't blinking anymore).
The first time this happened, the board appeared completely dead - the programmer wouldn't recognize it, and refused to flash it. After a few days and magic it started recognizing it again, and going through the motions of flashing my firmware, but the verification error persists. The location of the error hasn't changed, nor has the two values (0x01 vs 0x95).
Any ideas what this could be?