RF PCB design is a bit of an art. It is also unforgiving unless done right. Here are one or two tips from a senior RF designer: (1) At a minimum make sure that there is an unbroken ground plane. (2) Keep all traces as short as possible. Remember long thin traces are high inductances and can cause problems at high frequencies. (3) Keep power line traces as wide as possible. (4) Put in RC filtering in any switching power supply output leads. (5) Keep any noisy leads away from inputs and crystal leads,(6) Keep output leads away from input leads or risk oscillation.
(7) Use plenty of ground vias or ground fences. ‘Nuff said..