How to troubleshoot scren session auto exit

杨光洪 <[email protected]> Tue, 23 Jun 2020 22:50:15 +0800
Newsgroups gmane.comp.gnu.screen.user
Message-ID <CAPhkawE=PuKFAHh1XQaR78QxaQkO0PGqwRSrfvpORH4Z=GmJLw@mail.gmail.com>
screen version:screen-4.1.0-0.25.20120314git3c2946.el7.x86_64
os:centos 7.4

operate:
1.
screen -S 2020
ls
pwd
ctrl+a+d

2.
screen -ls
1 Socket in /var/run/screen/S-root.

3.
a period of time (for example, 15 min later), *scren session auto exit*

screen -ls
No Sockets found in /var/run/screen/S-root

How to troubleshoot scren session auto exit? is there log file ? tks