I do wonder if there's a problem in that area, sometimes it seems as if I have to tune up another 0.1Mhz on FM to get a better signal on some weaker stations. It does seem that Radio WM on 95.6Mhz is the worst affected by this, the spatter tends to be all over the 'dial' but worse in those middle sections.
I'm wondering about getting the SW1 sent off to be professionally refurbished, maybe see if they can source an aerial and battery cover too. I'm not proficient enough to do it myself, my soldering skills are certainly lacking!