The rear camera and LED flash seem to no longer function on my Sony phone. 1st step was to attempt firmware repair using the Xperia companion tool, but that accomplished nothing (other than a lot of wasted time reinstalling apps and data).
Today, I removed the back cover and checked the connectors. Connection was firm, and I didn't see any corrosion. An online search had a few people with a similar problem, which was fixed by replacing the camera module. Thankfully, it is fairly inexpensive, so I bought one today. Crossing my fingers that it solves the issue. I'd rather repair vs replace the phone.