The phase shifter was re-tuned before the final measurements to meet the field integrals tolerances. The change in field integrals happened between DS001 and DS002.
We didn’t measure off-axis field integrals for DS002-DS005, but there is on-axis change of a few G-cm between DS001 and DS006. 
It was enough to bring off-axis integrals out of tolerance.
The phase integral was checked at 15mm gap before re-tuning.
DS006,    15mm gap,  PI=6.8496
DS005,    15mm gap,  PI=6.8494
DS001,    15mm gap,  PI=6.8510
The change in PI (DS006-DS001) is small (2*10-4).
DS006,    15mm gap,  PI=6.828  (after tuning).