There was a known bug in earlier versions of the software that was similar to what you describe. However, I thought this bug was fixed during the internal alpha stage.

What version of the player software are you running?

More detail: There are certain audio filters that get applied to the AM signal, they are designed to make the normal characteristics of an AM radio signal sound more pleasing to the ear. There was a bug in one of the earlier software releases which caused these audio filters to sometimes be applied even when the selected station was an FM station. When this happened, it would make the FM station sound like an AM station, all tinny with no bass. Is this the bug you're describing?