Well I know for a fact that I did have my own 28Mhz WSPR decoding
at one point on whatever 10m random freq I chose for the test.
Then I moved to another, and it all went skew whiff.
I have no doubt that there is a problem which manifests itself
depending upon the actual chosen frequency of operation, and it only
takles a matter of a few kilohertz to send it into different set of
circumstances.
As Hans said, and I agree, there's got to be a mathmatical relationship
to this error, which shouild easily be sorted with the software code.
As I was taught many years ago as a rather green student at electronics,
that all faults are simple. It's just finding them that is the hard bit.
Never true'er ! ;-)
73 all de Andy