iPhone 6 flashlight problem

I bought an iPhone 6 for 50 euro that i knew flash wasn't working so i thought it was a bargain. When taking a picture it pops a flash, then shoots the photo, so its the same as shooting without flash. It also won't turn on as a flashlight from the control center, however it does with a 3rd party app. When recording a video , everything seems to work good. So i ordered a replacement part, changed it , nothing changed. I tried factory resseting the phone, nothing changed. Currently the iphone is on iOS 10.3.3, i don't want to update it to the latest 11.3 because of the performance issues it will give to iphone. What else could be wrong besides the software?