iPhone6s lcd connector flashed red?

Hi, so a friend of mine gave me an iPhone6s for me to try and repair.

The initial problem was that her screen was replaced by a phone repair shop in her hometown and two weeks after that the touchscreen was not working at all. The bottom half of it would not respond to touch and the top half would respond only every once in a while.

I have fixed mobile devices before and so I had the tools to open the phone. I did and I unhooked the display cables (3). I took a look at them and at the touchscreen, but I didn’t see anything wrong. I decided to plug them back in to check if maybe the problem was the cables not being attached properly. The minute I positioned one of them into its spot a square underneath the cable flashed red and the connector smelt burnt. I’m sure it’s not the cable’s fault as the smell doesn’t come from it but from the connector instead.

Any ideas on what I can do?