Receiver board changed its receiver frequency

I came across a strange problem today with a multi frequency receiver board, on a gate, which changed its frequency by itself, probably after a power glitch. All of a sudden, the remotes stopped working. They were all 433Mhz. The selectable frequency receiver was now working with 303Mhz remotes only! Power down and power up- 433Mhz resumed, remotes then worked.