Started print, and it started heating up. I thought it was working fine since 1.2.14 wouldn't even display the temperature curves after hitting Print. However, after canceling the temperatures continued to ramp up no matter that I tried to set them to off, and then to 0. I had to reset the RAMPS board, and unplugged/reconnected the arduino to the Pi to be safe.
I think this might be a bug that's unrelated to the one we're pursuing. Probably worth testing when we reach a stable point again.
I retried the print, this time letting it go through, and it started printing fine. I canceled the print, and the temperatures fell off on a curve like you'd expect.