Greetings, Espresso116.
I see that you don't want to use the Live Photos feature while taking a picture from the Messages application on your iPhone 7. You've turned that feature off in the Camera application and also under "Preserve Settings", but the Camera in Messages still shows you're taking a Live Photo. I'm happy to help.
Take and edit Live Photos -- Open the Camera application and make sure that it's set to Photo mode, then check Settings > Camera and be sure that "Preserved Settings" in engaged. Force an app to close on your iPhone, iPad, or iPod touch -- Next, close the Camera and Settings applications and -- Restart your iPhone, iPad, or iPod touch -- Once your iPhone has returned to the Home screen, open the Camera application and Settings, check that they're still engaged, then test the issue.
How to back up your iPhone, iPad, and iPod touch -- If restarting your phone didn't resolve the issue, please be sure to have a fresh backup to keep your personal information safe. In order to back up your Health data, the backup needs to be encrypted. iCloud does this automatically, but iTunes doesn't. If you'd like to use iTunes to back up your phone, refer to this article: About encrypted backups in iTunes
If you can't update or restore your iPhone, iPad, or iPod touch -- Even though the title of the article isn't specific to your issue, the section titled "Put your device in recovery mode and set it up again" will walk you through all the steps to reinstall the iOS software on your device. Test the issue once your phone has returned to the Home screen.
Let me know how that goes.
Take care!