I bought a relatively cheap clock-radio a few years ago. I have three, all set to come on at different times for different shows I listen to. The newest gets the worst signal on 1280. But it got even worse after daylight savings time ended. I blamed that on increased interference just before sunset. But then one day another clock-radio was having trouble too. I adjusted the frequency and that seemed to work. But I had never touched it. I found out what was wrong with the other one when I heard a station ID that included 1290. I had never touched the thing!
The mechanical lash in most inexpensive radios is so poor it is hard to tune a high band station. I wouldn't be a bit surprised if you had a radio with some mechanical drift - maybe in a wrongly tensioned spring somewhere.
If it is an electrical problem, it is most likely in the converter coil. Many years ago - I had one go bad and the radio would drift all over the place and had a "swoosh" in the audio.