[Elecraft] K3: changing modes changes the frequency?

[Tom Blahovici]

Hi
In comparing two k3s I am seeing completely different behaviour of the vfo a when modes are changed. 
If for example on one radio I am tuned in to wwv 10mhz, using am,  the frequency on the radio shows 10.000.000 as it should. If I then change to cw, the radio all of a sudden reads 10.000.680.
The other radio does not do this it stays at 10.000.000. 
Which menu option governs this? 
Can't find it! 
Thanks,  Tom