If the conditions are either substantial changes in sound quality between the HD and analog FM, or time-shifting, it is not the radio. It is the radio station's implementation of the HD radio signal. Not only do many radio stations broadcasting in HD give very little attention to the technical characteristics of what they are broadcasting over HD, but also many radio receivers deal with the HD signal in different ways. If he HD part of the signal is not set up according to the HD specifications, it can cause significant issues in receivers. Unfortunatley, most radio listeners will not complain to a radio station when there is an issue, believing instead that the problem is in their radio. Also, there is simply not a sufficient base of HD radios in most markets for significant numbers of listeners to be affected by a poor HD implementation. About two years ago I had a similar annoying issue with one of the top radio stations in Washington. After the radio station went back and forth with the iBiquity (HD) engineers several times, they finally came up with a wrong implementation of the HD signal at the radio station. So call the radio station, ask for the chief engineer or operations manager, and complain.
Agreed -- though what's annoying is there seems to be no way to force this radio to analog mode to alleviate this condition. I've personally had it happen (it's quite irritating) -- but it's generally only one radio station (in my area).