Touchscreen ist not reacting, sometimes

Hey guys,

I have a problem.

After I restarted my iPhone 5c I had first some little truble with the touchscreen. Sometimes it was not working (touch) and sometimes I worked fine. Display was always okay, only touch had problems.

Then it got worse and the periodes of working touchscreen got smaller. I replaced it in the store, it worked and 1 day later, again it started not do work.

I paused using the phone for some days, put back the old screen (also been replaced 1/2 year ago) and it worked 2 days. Right now, again, its not working for most of the time.

Might it be someting like a loose connection? I checked the connector for the digitizer by eye. Everything looks all right.

What could it be? Cause I changed the display, with the cables and it also didn't work.

You'd do me such a favour helping me.

Thank you so much,

Leo