idxmin() changes the coordinate labels on my plot

[paniash]

Hi,

I recently started using xarray in my work and came across this issue where after defining the coordinate labels for my dataset (see below for example), when using idxmin() method function, it seems to change the label for the coordinate that was originally set to "Probe frequency" to "VNA_ch1_ch1_frequency". How do I fix this? Thanks.

_ax = plt.figure().gca()
_y = (d9["VNA_ch1_magnitude"]
      .assign_coords(VNA_ch1_ch1_frequency = lambda x: (x.VNA_ch1_ch1_frequency * 1e-6).assign_attrs(long_name="Probe frequency", units="MHz"), 
                     Valon_CW_frequency = lambda x: (x.Valon_CW_frequency * 1e-9).assign_attrs(long_name="Heater frequency", units="GHz")
     ))
abs(_y).T.plot(ax=_ax)
abs(_y).idxmin("VNA_ch1_ch1_frequency").plot(ax=_ax, color="red")
_ax.set_ylabel("Probe frequency [MHz]")