CP6 overfilled following today's LN2 delivery -> This is uncharacteristic for this system (CP6) -> Investigation shows everything is nominal except that the dewar 25 psi < vapor pressure < 30 psi which is ~10 psi greater than normal for this system -> I observed that the manual blow down circuit was frosted which indicates that it was used to vent the displaced vapor during the fill (as expected).  It may be that the fill rate is too high resulting in the larger than normal head pressure increase for a fill(?) -> PID response too slow for rapid change(?) -> I decreased the time between PID samples from 50 sec to 20 sec -> Today's driver is associated with past irregularities -> I'll investigate if this driver is doing something different from the other drivers