Help identifying drop in ssignal

I wonder of anyone can explain to me (as an almost novice) why the pcb I am working on is experiencing a loss of signal. I am converting a board of RF 153.050 to 153.350 MHz and have changed one of the crystals appropriately. However, the signal is now experiencing a drop out, an occasional surge. Aside from that, it's not tuning to the frequency particularly well either using the oscillators. As far as I was concerned, changing to the correct crystal should have been enough to modify the frequency slightly.

I am completing a task way out of my depth so what I have written may not have made sense! I'm just wondering what components you would check to solve the problem. I'm certain it will just need a slight change of component elsewhere as the person who designed and made this will have made it perfectly. They are no longer around, so I can't ask them.

Any ideas?