Hi i have Condor P8 lite … and i think it is Vivo xl2 .. this happens to me too .. i thought it was hardware thing .. it costs a bit to change the display entirely .. so i rooted my phone and deactivated the hard buttons and activated the soft one .. then one day i got bored and found out that there was a MIUI9pro custom rom for my phone so i tried to flash it .. something went wrong and i got a bootloop .. i couln’t shut it down to flash it again .. so i had to open the phone and unplug the battery then plug it again .. and i flashed MIUI9 (it is amazing btw) xD and unexpectedly .. the problem was solved .. after 3 weeks .. today i had the same problem again .. randomly exiting apps etc etc .. so i did it again .. unplug the battery the plug it again .. not take it out ;. just unplug it .. and it is half a day and the problem is gone now …