iPhone XS Max back camera not working

Hello! I’ve recently bought an XS Max (this was off TradeMe, like a New Zealand eBay if you will) and the back camera chooses when to work lol. By this, I mean the back camera will only work for Instagram & Messenger when wanting to take a photo, whereas on the default camera app pre installed on to Apple phones, the screen turns black. Snapchat and other social media apps don’t give me the option to ‘flip’ the camera from selfie to back camera. Also the flashlight doesn’t seem to work but when videoing on Instagram with the flash on on the back camera, it works. Now I’m not too sure if this is just a problem with my phone, or whatever, but it’s weird how my back camera works for IG & Messenger only and not other apps. Was hoping to see if there are solutions to this? I’ve tried turning off Voice-over which most online guides covered but still nothing. But yeah again, was hoping to look for some solutions before I result to factory resetting my phone.