While it shouldn't lose it's settings, it's hard to say what happened. I'd clearly reprogram it first and see if that fixes it. I have had one other person contact me with a similar story. The calibration is stored in the uP FLASH, and should be there until changed.
It it's forgotten it's calibration, it could be an issue with the microprocessor parts, though they're normally really reliable. I'd also check the wiring to make sure there's not a suspect connection. For instance, losing it's ground can cause issues with the board.
