create_surf_distance_log acting funny

create_surf_distance_log gives different results than get_surface_picks and points.snap_surface.

Possible error: Wrong alignment of active values in the surface and the distance calculations:
If points.snap_surface is run with activeonly=True then 5485 values are reported. That is where create_surf_distance_log stops when calculating the difference.

The code:

import roxar
import xtgeo

TRAJNAME        = "Imported trajectory"     
LOGRUNNAME      = "planned"          
CAT             = "DepthSurface"          

print(xtgeo.__version__)

well_name = 'FB2I-1V3'
surf_name = 'Heimdal_top'
surf = xtgeo.surface_from_roxar(project, surf_name,CAT)

#The preferred way (for me) to calculate a distance from a well to a surface
well1 = xtgeo.well_from_roxar(project, well_name, trajectory=TRAJNAME, logrun=LOGRUNNAME, lognames=['MD log'])
well1.create_surf_distance_log(surf,'diff')
well1.dataframe.to_csv('well1.csv')

#Where does it cross according to get_surface_picks?
picks1 = well1.get_surface_picks(surf)
print(picks1.dataframe)


#A workaround using xtgeo.points. Gives same results as get_surface_picks()
well2  = xtgeo.well_from_roxar(project, well_name, trajectory=TRAJNAME, logrun=LOGRUNNAME, lognames=['MD log'])
points = xtgeo.Points()                                        #Empty point set
points.dataframe = well2.dataframe.copy()
zorig = points.dataframe['Z_TVDSS'].copy()                     #The original TVDSS.
points.snap_surface(surf, activeonly=False)                    #Now the surface TVDSS is put into the Z_TVDSS-column
                                                               #Using activeonly=True gives just 5485 values but then the next line will give wrong results.
                                                              #Is this what happens in _create_surf_distance_log_ ?
points.dataframe['diff'] = points.dataframe['Z_TVDSS'] -zorig  #Calculate the difference
points.dataframe.to_csv('well2.csv')

The printout:
2.15.2
X_UTME Y_UTMN Z_TVDSS DIRECTION WELLNAME
0 475590.725685 6.565440e+06 1726.864474 1 FB2I-1V3
1 475482.763505 6.565435e+06 1733.803068 -1 FB2I-1V3
2 475201.817559 6.565473e+06 1741.790771 1 FB2I-1V3
3 474380.514290 6.565967e+06 1740.946156 -1 FB2I-1V3

The difference in the resulting files

Reproduce the discrepancy with the supplied script, starting with Well.create_surf_distance_log and comparing its active-value handling with get_surface_picks and Points.snap_surface(activeonly=True). Use the reported 5485-value result and the generated CSV files to trace the alignment; done means the distance log and the two comparison approaches produce consistent results.