James Cohen wrote: "Yes it was replaced at the Apple Store and the max capacity is 94% as of right now."
Good.
"Why do you ask? The camera worked fine with a 4 year old battery at 60%."
I ask because a battery weakened by age & use, or a non-genuine iPhone battery can cause a variety of strange issues. So when an older model iPhone such as your "8" has issues, it's reasonable to ask about the battery – even if only to rule it out as a possible cause.
Also, the long process of applying an iOS update to an old iPhone with a weak battery can be the proverbial "straw that broke the camel's back." We see a lot of posts here blaming an iOS update for causing issues. Then, when asked about the battery's maximum capacity, the true cause is revealed to be a weak, aging battery.
...But unless the Apple technican was careless during your battery replacement, the battery can be ruled out as the cause of your issues.
"The likelihood of all these iPhones randomly having hardware issues at the same time and coincidentally within a few weeks of updating to iOS 15.5 is pretty low."
As there are millions of iPhones in use, the likelihood of similar hardware issues appearing at similar times is pretty high.
Apple says that there are charging issues with iPads updated to iPadOS 15.5. [Source] ...So, in a similar way, it's quite possible that iOS 15.5 has caused the Back Camera and Flashlight issues in your iPhone.
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