I love my iphone but if it costs
I love my iphone 6+ but if I pay $700 for a machine that costs so much more than most android competitors I expect it to be so thoroughly tested the basic functionality of camera hardware/software would never be an issue. Time to get a new supplier/revamp quality control Apple.
How do you test something that fails months into the future?
You can't you can just fix it for the client and then see what can be done upstream to prevent something like that in the future.
The supplier in this case is Sony, the same one they've had for years
Sony is a major sensor producer and supplier to smart phone makers, there aren't that many top notch options here.
BTW, the Iphone 6(not +) doesn't have this issue.
Sony's module is built of many parts, which themselves come from other suppliers.
This could be either a design failure from Sony (part fails because it wasn't designed properly),
or part fails because of manufacturing issue at a Sony supplier.
A design flaw is usually worse than a manufacturing flaw, because a manufacturing flaw won't affect many of the phones, a small number of a batch would have the issue (this seems to be the case here) while a design flaw would affect all of them.
Finally, why should Apple go elsewhere?
Is there really the certainty that a random sensor maker will give them both a module with both a better reliability and a better performance, than one they've had a relationship with for years? Not at all.
Believe me, Sony knows they f-ud and Apple will make them pay for those replacements in some ways and they'll surely not repeat the same thing again.