Why is my display blinking?

Hi everyone!

I've broken my Z3C back glass and lower speaker. Got spare parts from eBay, then replaced it following your instructions.

As I've fixed many iPhones and other phones I consider myself experienced in it and this replacement was one of the easiest ones.

Anyways, after putting everything together I started it up and the display was a bit dimmed in the right bottom corner and blinks when I push the back glass. Even just a slight force is enough for it to blink.

Can't find any relevant answers on the net, so I am turning to you with this Q.

Thanks everybody a lot for the tips!