Symmetrical quadrupole device of dc

When I was using dipole in dc, I tried to change it to a symmetric quadrupole, which can be measured, but two sets of data are 0 (there are 0 values), I don’t quite understand why, does anyone understand, thanks, the data file seems to be impossible to upload.

uploading your script would be useful, othetwise it is hard to identify what you are asking for.