I believe you got it figured out according to Larry.
I would be curious what method you used to measure the frequency and determine it was off by a few hertz? They are calibrated using sophisticated equipment and if by “few” hertz you mean less than 20 or 30 Hertz, that is one thing. If you mean 200 or 300 that is all together different. What piece of equipment did you use to measure the frequency? Was it the transmit frequency or the receive frequency?
If you altered it, did you alter transmit and receive or just one?