Trouble answering phone calls sometimes

[mariusfilip]

Hi, Htc M8 owner, Lollipop 5.02, rooted, xposed, sometimes when the phone is ringing, the incoming call screen shows up but it is unresponsive, sometimes the screen is black when ringing, i made sure that the proximity sensor is not covered, I'm using it naked, i cleaned system and dalvik cache many times but still the same problem , it shows up the 'send/don't send error' to htc when this happens.
Has anyone else had this problem?
I'm trying to find out if it is a hardware or software problem, the only real solution i see is to bring it back to stock to see if the problem persists.Thanks