It would be good to see pictures of the notches. However, even without seeing the pictures, I would say that this looks like a problem with the SYM adjustment on the 3 MHz filter board. If the problem appeared suddenly, it may be a failed adjustable capacitor. If it showed up slowly, the filter probably needs adjustment. You will need to build the 3 MHz crystal bypass networks in order troubleshoot and adjust.
Still, it would be good to post some pictures before you take my word for it.
Vladan
