DSG constraints by world coordinates longitudes as West longitude returns an error

Making subsets using /X= /Y= on the PLOT command for DSG data isn't consistent.

yes? use WestCoastCarbon_profile_dsg
! this works correctly
yes? plot/x=-121.5:-120.5/y=33:35 pco2

This is the same region but returns an error

yes? plot/x=121.5W:120.5W/y=33:35 pco2
 **ERROR: illegal limits: "PCO2" does not exist at X=121.5W:120.5W
          Axis extremes are X=122.6188W(-122.6188):117.6313W(-117.6313

Timeseries examples work inconsistently

yes? use pmelTao5daySst_timeseries_dsg

yes? ! This is correct
yes? plot/x=120w:20w t_25

yes? ! There are profiles in this range, but we get an error and strange values
yes? ! for the valid range
yes? plot/x=-170:-150 t_25
 **ERROR: illegal limits: "T_25" does not exist at X=170W(-170):150W(-150)
          Axis extremes are X=2.5362W(-2.5362):7.4638W

Trajectory datasets do not show this issue. (Testing data in the southern hemisphere also looks correct.)

yes? use socat_trajectory_dsg
yes? plot/x=170w:160w/y=55:65 temp

NOAA-PMEL / Ferret

DSG constraints by world coordinates longitudes as West longitude returns an error #1954