When only one filament is loading, another filament is unloading at the same time. (NOT unloading, then pressing again and loading). Then when one unloads, a different one loads simultaneously. I do not think this is what is supposed to happen.
Thanks in advance.
Despite you saying that it's working, I would 100% guarantee that it isn't clocking it at 90 degrees... or the selector cam is damaged/not aligned properly or lastly, the bearing are not in place. There is no way it can drive two filaments at the same time if that weren't the case.
Make sure it's a) turning in the right direction, b) doesn't have a damaged cam, which can happen if you happen to accidently swap the motors and try to home it, c) isn't homed before the start of every print, d) don't have the proper timing in the pauses (G4) commands.
And finally,
e) Actually, now that I say that... all the above is assuming good printed parts... and that's key... the parts must all be printed on a single plate and in the same orientation to get the proper lengths... if they're not even .25mm different, then it can cause issues due to the gap between active and active filaments being as small as .5mm.
Bill