EF Lenses on R Mount (f/1.2 portrait primes)

CESA wrote:

But Nero two other questions:

1. If the lens turns out to have and adjustment around +17 does it means that there is some mechanical or electric mechanisms that is failing?

I don't think the mechanism is failing, but if you require a considerable adjustment, it means that the lens is within spec but needs a calibration to be applied.  If you feel that +17 is too much, then you'd be right thinking it's pushing the boundaries of what is acceptable from Canon.

2. If it turns out to ave that calibration, does it mean that in another camera DSLR like 5DMKIV will have that same adjustment?

Each camera sensor will be slightly close or further away from the back of the lens.  So each camera will need to be calibrated for the lens.  It's probable that the distances will be similar but they won't likely be exactly the same.  When you make an MFA adjustment calibration, it has no effect on the lens, only the body of the camera being used.  Since each camera has its own limitations and variations, you will have to calibrate each camera with an f/1.2 lens.  The MFA adjustment will be similar between cameras using the same lens... but not exactly the same.

3. Even if this lens has got this adjustment on a DSLR, if I go to EOS R or mirrorless camera the lens will not need any adjustment but the fact that had to be adjusted on the DSLR will it likely mean that it will potentially have a problem in the EOS R or mirrorless camera? Do you know what I mean?

I understand.  But with mirrorless, the sensor is used to calibrate the focus.  Remember your MFA adjustment with a DSLR + lens requires a shot taken with AF using the Live Preview? Remember how this is your test shot to be used when comparing it to the OVF shot?  The LCD shot ought to be in perfect focus.  The same applies to the use of an EOS R (or any mirrorless camera with the same lens).  All shots taken with mirrorless cameras should be problem-free.  The AF will also be more accurate with cameras like the EOS R because of the new DPAF sensor.

4. Imagine that he lens is sent to Canon- can they bring and fine adjust the lens itself if it is a problem with the lens in the sense that although it has passed the control it was close to the limit spec, they can bring it to the best spec which is supposed to be close to 0% if the tolerance is say +-5%. Do you know what I mean?

When you send in your lens to Canon, they will insist that you send your cameras in with the lens.  They calibrate the cameras for each lens.  They use the MFA to do this.  There's nothing inside the lens that they can modify.  There is a microprocessor inside each lens that communicates with the camera and this can be replaced if it fails. The lens elements can also shift if the lens is struck or dropped.  Sending any lens into Canon almost inevitably results in it being returned with a different problem... like corner softness or softness at specific focal lengths.  Only send a lens in for repair if it has been damaged.
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Professional photographers often send their cameras and lenses in to Canon to be calibrated using a Calibration tool similar to the FoCal one.  Again, the process used is essentially the one you can do yourself at home.  It's extremely rare to get a defective lens when you buy one brand new because Canon have a testing process for every camera and lens before they leave the assembly floor.  Anything that fails to test correctly is re-purposed or recycled for parts.  If you calibrate your lens using the MFA tool in your DSLR - and it still doesn't lock focus accurately - return it.  If it does appear to focus correctly afterwards for 96% of your shots, then the lens is probably fine.  Put that same lens on an EOS R camera and it will probably be 99.9% to 100% realiable.  Bit if there's a fairly high rate of out-of-focus shots still coming from it after FMA on your DSLR, return it.