So I took my 6D II into CPS for service. It was front focusing pretty hard and I couldn't get it micro adjusted. Canon sent an invoice stating exactly "focus points are off, unit is front focusing, unit requires electrical adjustments to the AF sensor." Does this mean they're just micro adjusting it themselves? Was this something I could have done or does it require an expert?
Based on my experience with CPS, that summary on the invoice was written before they actually looked at your camera and was adapted from your description when you sent it to them.
The technicians at Canon's Factory Service facilities have access to areas of adjustment within the camera's firmware that are not available to the end user (at least not without hacking the camera's firmware). They can probably adjust the AFMA in a greater range and center the 'zero' point in the AFMA adjustment available to the end user via the camera's menu so that it is closer to the needed adjustment with either your lens (if you sent it in as well) or a 'blueprinted' lens (if you didn't include your lens).
Is this ideal? Probably not, because it means the PDAF sensor may still be a bit further/closer to the lens than the imaging sensor is. But it is a lot easier (and thus cheaper for the service center to do and ultimately for you to pay) to do an electronic adjustment than to mechanically adjust the PDAF sensor. If it solves your issue enough to get your camera within Canon's range of tolerances it is considered 'good enough' by Canon.
Also based on my own personal experience with CPS/Canon Factory Service:
When a repair is invoiced as 'electrical adjustment' it doesn't always come back with the actual problem resolved.
I had a lens that was demonstrating slight tilt and sent it in with a general "lens is out of alignment" and "focus is inconsistent" description. They 'electrically adjusted' it and sent it back. The alignment issue was no different than before. The only thing I could tell they did was to slow down the AF speed of the lens.
A while later and after a hard impact the alignment issue was worse and I sent it in again. This time I included example photographs taken with the lens on two different camera bodies showing the severity of the problem as well as photographs taken with one of the same camera bodies and another, similar lens that did not show the issue. I also requested they reset the AF speed to factory defaults, as that had not solved my problem when the lens had been sent in earlier. The second time I got the lens back aligned properly and the AF speed set back to the original speed.
- Include as precise a description as possible as well as example images that demonstrated the problem and example images that eliminate other pieces of the puzzle from being the cause of the problem.
- If the issue isn't fixed the first time, contact them and insist they do it again and fix (at no additional charge) what you've already paid for them to fix!