In a variety of programs and apps, but most often text messaging, my Galaxy S4 just stops responding to my touch on the screen (and sometimes even pressing the home, power, or volume buttons). Other times, it reacts very slowly. I have tried adding some apps to address potential problems, all from CleanMaster, like junk cleaning, antivirus, battery saver, etc. I don't know if it's working or not. It doesn't seem to be.