IPCHI2 changed between versions (Run1/Run2)

When filling a tuple from stripped data DSTs it seems as if different DV versions are giving different values for the IPCHI2 of the tracks. All other variables are identical. I attach a sample DV script. The two versions I tried are v39r1p6 and v45r7. E.g. for v45r7:

            B0_M  Pi_IPCHI2_OWNPV  eventNumber          Pi_P        Pi_PT
0    4980.026908        29.096502      1017907  13211.904201   847.406945
1    4951.763726        12.297061      1017907   9335.603953   269.956065
2    4974.812961        16.781354      1463846  10702.625685   794.707409
3    5257.907759        21.540463      5477292   5978.041795   281.295015
4    5450.389711        78.265598      5477292  29013.281582   929.454447

and v39r1p6:

            B0_M  Pi_IPCHI2_OWNPV  eventNumber          Pi_P        Pi_PT
0    4980.026908        28.660212      1017907  13211.904201   847.406945
1    4951.763726        12.272164      1017907   9335.603953   269.956065
2    4974.812961        16.832627      1463846  10702.625685   794.707409
3    5257.907759        21.540463      5477292   5978.041795   281.295015
4    5450.389711        77.527634      5477292  29013.281582   929.454447

b2xmumu_run1.py