(Disclaimer: this is just my personal current understanding of the WFTDA rules as of Feb 2015. It doesn’t represent any kind of official position from any organization)
New as of the December 2014 rule set, a 4 point pass will sometimes creep into what used to be scored as solid 5 point pass after 5 point pass. This happens after a power-jam situation given that Not on the Track Points (NOTT points) and Jammer Lap points are mutually exclusive and who is lapping whom resets when the penalized jammer re-enters. Which pass exactly gets the 4 points depends on the scenario.
Scenario 1: Red Jammer gets the NOTT point (18.104.22.168.5) in the pass where Blue jammer returns behind her. If Blue jammer gets stuck in the pack, on her next pass Red Jammer is not technically lapping her yet and won’t be eligible for a Jammer Lap Point (7.2.8). So, 5 points and then 4 points for Red.
Scenario 2: Red Jammer does not get the NOTT point for Blue jammer, but DOES put herself in lapping position. If Blue jammer gets stuck in the pack red jammer will get the Jammer Lap Point on her next pass. So, 4 points and then 5 points for Red