I’ve received my unit quite early in the release procedure (thank you, argon40!). So I’ve missed the now available wiki entry regarding setting “dtparam=ant2“ in
/boot/firmware/config.txt when setting up the argon one up. This is for switching the wifi antenna input to the CM5 U.FL connector, which you should use with the argon one up shell.
Please check, if you have such entry in your config.txt. If not, wifi signal strength will be sub-optimal inside a such beautiful metal case 
HTH
NightHawk