the passcode thing seems to be after egz0.22 has been installed, and than going back to the stock firmware, due to the k6 not taking egz correctly and getting the pixel screen of death on power up than using cps to to program the radio i never had that issue with ijv i went back and forth with it never a issue the qs12345 passcode does not work, its one, someone else has written into their the firmware . on my first k6 that did this. before i found this thread, i contacted quanshen via a fb group they are in they unlocked my radio a via remote hook up, they told me they do not use any type of passcode for cps to work with the k5 or k6 models only higher up models that should not be unlocked by the average user, business radios etc so like say a employee cant unlock the radio, and its only on what frequencies it should be on. and was strange it was on the radio, he asked me if i had added it and forgot the code told them "no" and told him what i had done with using a modded firmware for experimentation . it took the tech about 10 mins to get it unlocked he said after using a few passcodes they use to unlock radios he said had to use a special factory code they have that will unlock any model they have for fixing either a bricked radio or some other issue it finally unlocked. and was not qs12345I use CPS stock v.1.0.38 and K5prog_win V0.1,27, both on windows 10 with no issues at all.
Firmware is stock or IJV.
I have never encountered a password situation but a remark on Quansheng website says try qs12345.