proberly just bad luck as they seem to be able to focus the rear cameras fine, and i assume they are done under same circumstances.
I have to admit i had the belief the lens module was tested plugged into some jig with HDMI output, but thiss offcourse can be problematic with a camera unit mounted on the Main PCB.
And working with this myself experimenting with IP / CCTV and action cameras i know its just a matter of turning the lens 10 degree and then its in focus.
Its hard to do by hand, i have done this with my C1, and allso experimenting with my mobius as i cant get either of them to work as webcams.
So i have to ajust a couple of degrees in segments, and then take SD out and preview footage on computer, trial and error, i normally focus on a pice of modeltrain rail or the power mesuring gear on the wall, both about 3 M from my seat in front of the computer.
And then verified by filming a sign on the street in front of my apartment, and the licenceplates on the cars parked in the yard witch is about 10 and 15 M avay ( using digital zoom to verify best possible focus )
Quite time consuming that way, but its that way or too blurred footage on my cameras.