Red Screen/ Boot Loop

I recently bought an Iphone 6 Plus off of ebay. It was in two parts and I decided it was worth a punt as I've been fairly handy with replacing parts on a few other iphones I've gotten my hands on.

When it arrived the first thing I noticed was the inside looked pretty clean, there is no water damage, and all the connectors look like new. When I connected the Flex cables it turned on and immediately went into a bootloop. I tried putting it into recovery mode and all that, except it doesn't seem to respond and my computer won't detect it. I thought it might be the battery, as I have seen that can put the device into a bootloop. It now stays on a little longer, and seems to end up in a red screen.

From a little research this might be the proximity sensor. After a litle further looking around, there is a slight tear in the actual digitiser cable, or the flex cable closest to the North/Top of the phone.

My question is if anyone has any experience with this issue and whether a tear in the digitiser cable could cause a red screen? To be fair it looks like the whole lcd has had the glass replaced pretty poorly, or could be a cheap replacement.

Any help/advice is much appreciated!