Game restarts when switch to another App/Game

Iam using Unreal Engine 4 to create a game. The game runs fine on phones but for some reason when I switch to another App/Game and go back to the game Iam developing it always restarts (does not pause). Locking the screen works fine.

Any ideas if this is a phone setting or something I have to figure out inside the game engine? I have tried with developer mode on/off.

Thanks