Learn the reason for Mobizen quitting and exiting
Mobizen Screen Recorder, like any other app, takes up Random-access memory (RAM) to run. When you exceed your device's capabilities, your device will act in an abnormal way.
A Little More Information
Due the LMK (Low Memory Killer) policy by Android, if there is a high volume of memory usage, all other apps except the currently running one will be automatically closed.
Ref. What is LMK? (http://ajqi.com/)
How to Fix this Problem
Close all apps except Mobizen app and the actual program to be recorded.
Find out more on how to fix this problem here.
Note! Some devices will not act normally due to the fact that it has less than 1GB of RAM.