Default [Q] Is it possible to break the touchscreen without damaging the display?

Replaced the glass on my s4 (home job) thought I was super careful and the display is totally fine, however now there's times when the touchscreen is buggy- some areas wont long press, some wont respond, everything lags a bit, but then sometimes it works fine. Could it be a rom issue or is it my digitizer that I will need to get a complete replacement for?