It sounds like there might be a connection between the iPhone X back camera failure and the front TrueDepth sensor system.
Third-party vendors might not be able to absorb the lower cost of iPhone batteries like Apple can.
Apple recently decided iPhone screen repairs by third-parties don’t fully void your warranty anymore. Affected iPhone will also qualify for warranty coverage as long as the repair isn’t related to the third-party display itself. Before, iPhones with third-party displays weren’t eligible for authorized repair under warranty from an Apple Authorized Service Provider.