Low backlight after display replacement!

Dear folks,

Yesterday I managed to replace my Iphone 5S display after my daughter crash the old one (lol).

It's pretty easy to do so, BUT, after the replacement my screen start some kind of flikering. Removed the display connector and assembled it again solve the issue.

Today I realized that the screen was a little bit darker than the normal. Got my boss 5S and compared with mine and it is a little darker than the normal display.

Now I'm confused: Could it be a poor quality display or a bad connection between the board and the flat cable (loose connection)?

Cheers!

Carlos Brida