Screen replacement - black screen

I smashed my phone and it wouldn’t respond to HDMI output, let me sync with my laptop or make any sort of noise. I bought a £20 replacement screen off eBay and fit the new screen myself. However, the screen wouldn’t display anything but black. The phone would light up and black screen and allowed me to get on it to recover photos - it worked with HDMI, keyboard and made noises etc. I kept trying to get it to display something by removing and reinstalling the new screen...nothing. Then while the screen wasn’t attached to the housing properly it lit up and displayed correctly...until I lifted the screen slightly and GONE. It has done this very intermittently, having displayed the screen for a few seconds every few days. What could be the issue here? Is it the screen or the phone? Do I need to get a better screen or clean the housing? It can’t be the logic board cause it still works, it can’t be the screws because they were put in correctly. The strange thing is that it has displayed a set of blue lines at times. I want to know whether it’s more cost effective to bend the case back and fit the screen or claim on insurance? Thanks a lot