Hello Matt,
Do you have any cellular towers nearby your ePMP equipment? Some ePMP users have complaint in the past about potential interference from cell towers.
Increasing your holdoff timer may alleviate the situation.
Also, out of curiosity, are you using the old ePMP1000 GPS antenna with the ePMP2000 or are you using the GPS antenna included with the ePMP2000 radio? The new antennas have better filtering/gain than the old one, plus they will allow the GPS chip to also use GLONASS satellites for tracking.
Regards