User Logout Unexpected

Users are getting logged out with this message “You have been logged out because your session has expired.” but at that time We can see cookie value in the browser and also can see session value in Memcached.
There is no error in an application and It is happening whenever the user uses the email module and Global Search.
We have two application server and Memcached installed on both servers to save Session in Memcached.

Below is php.ini configuration of app1, same we have configured for app2 also to save the session in Memcached.
[th]Local Value[/th]
[th]Master Value[/th]
[td] app1ip:11211, app2ip:11211[/td]
[td]app2ip:11211, app1ip:11211[/td]

SuiteCRM Version: 7.8.3
PHP Version : 7.1.7
Apache Version: 2.4.25

We are unable to find what could be the issue. Please help me out as soon as possible, As users are facing this issue continuously.

  1. Make sure you have available disk space in your server. Running out of disk space produces this error.

  2. Check the ownership and permissions in your session.save_path. The values that you show for this setting look strange to me; they should be a filesystem path, a directory where PHP saves sessions files…