why my Unity Android game close at random time after start on some devices.

I am developing a android game using unity. It workes properly when i use unity remote for testing.But when I build and run the game on the same device which i was using with remote,the game stops working and closes at random time.

these happens only with some devices ie Motog and Motog2, while with other device ie Motoe, Samsung duos it workes properly.

please help.

check if there is any exception error
too many exception error closes the game on android devices as an instance null reference exception