when there is some kind of percentage of flawed cameras i call it a series issue.
And what is that percentage?
I reckon Canon have sold at least 10's of thousands of 70Ds. Probably 100's of thousands. Canon have sold in excess of 5 million DSLRs since the 70D was released. Even if the 70D was only 1% of that, it would be 50,000. But the 70D is a top seller according to places like Amazon and BCN, so it is going to be more.
Meanwhile, how many have faults? Well 10's possibly 100's have stated they have a fault in forums and elsewhere. i.e. a very tiny percentage. But as ever the silent majority who don't have faults don't post that fact.
It's a real bummer for people who have a problem with their camera, and Canon don't seem to be doing a good job of fixing it for them, or managing the situation.
But I find no evidence to suggest that a high percentage of 70Ds have this fault, and certainly no indication that it is some inherent design fault or firmware issue - otherwise everyone would be reporting it as we all have the same hardware and firmware.
I have tried every way I can to find this fault in my camera but it stubbornly refuses to mis-focus. What I did find though was that every one of my lenses required some MFA on the 70D.
If there is a fault it is in the assembly process that appears to allow the build of misaligned cameras or the calibration routines are at fault, and in the testing process for not spotting them before they leave the factory.