Thin black line in photos

I don’t know what “a lot” is, but with over 1 billion iPhones no matter what problem you have it is almost certain that others will have a similar symptom. I haven’t seen any posts about it, and neither of my family’s iPhones show it. So unless several hundred thousand users report it I doubt there is anything for Apple to fix, except to treat each case on a case by case basis. Have you contacted Apple support about it? You can use the Get Support link at the top of this page. That will also allow it to be logged, so Apple can determine if it is a general problem or something with a few phones.

Have you tried any standard troubleshooting steps, such as restarting your phone?

I haven't seen any posts about this. And one would think if a LOT of people had such an issue, this being the worlds largest forum about iPhone, we'd see other with such an issue. I certainly have no thin black lines in any photos on either of our iPhone's. Perhaps you could post an example of what you're seeing?