Apps are closing on their own

[AC Question]

I got my Galaxy Grand's display changed after it broke and ever since I got it changed.. my phone behaves funny. The back key doesn't work. and the apps in phone close on their own. The battery drops .. but this is only when I am using mobile data. The phone works fine on wifi!!!! any suggestion abt what the problem might be?

 

[VidJunky]

You say you "got" the display repaired and now things aren't working correctly. I wouldn't worry about what the issue is where you got the work done should be handling this as a warranty of their repair. The "back" button alone is grounds for return. As for your issues, IMO, it sounds like the digitizer may not be plugged in all of the way causing misreads with the touch location. This could cause the back button to seemingly be pressed when touching other areas of the screen closing apps and not appearing where it should be. Just a guess but I'd take it back.