iPhone 5 power button not responding evenly after flex change

My Iphone 5 power button is not responding evenly on both sides, i changed the power button flex cable 3 times now and same problem?!!! i tried different adjustments and alignments on the back bracket like stick the button to right a little bit or to the left and no hope?!!

i tried to but some double sided sticky tab between the button and the back bracket to raise it up a bit towards the outer button and to hold it in place, but with no success.

If someone sure enough that the problem is with the flex cable or any other part please let me know, or if anyone had the experience doing this repair can guide me through this problem.