changing the redshift in velocity space

[Wang Chen]

I am trying to change the redshift from 0 to 0.12, and the code works well in wavelength space, but when I switch to velocity space, then after I execute "sg.make_spectrum(ad1, lines=[ 'O VI'])", it shows that "Setting wavelength of velocity center to O VI 1038 line at z = 0.000: 1037.613 Å.", which means it does not really shift the redshift to my desired values here, and in the output file there is no signal at all. However, I checked all my fields about redshift in the .h5 file and they are all correct, and also as mentioned above it works well for wavelength space but this issue only appeas when I switch to velocity space. does anyonw know why? thank you!