We determined that there was probably issue with timing in the pic. The timing problem seemed to be caused when the pic had received characters and entered the appropriate routine to flash lights and/or flip relays and another message came in while it was in this routine. One solution was to change pics and go with one that had built in UART. This meant that the receiver would receive all the time and be unaffected by interrupts. Due to the fact that the hardware circuit was already designed and built we decided to try a software solution to the problem.