Can you check session timeout settings in php ini?

session.gc_maxlifetime: 1440

Or is there another variable?

This is most likely a server issue. A possible reason is that the session lifetime is modified by another application on the same webspace.
Check out https://manual.limesurvey.org/Troubleshooting

I'll have a look through the trouble shooting guide, thank you. However, it doesn't quite add up to me yet since version 2.whatever I had installed before worked fine on the same webhost.

I had a look at the trouble shooting guide. Nothing that I see related to this I'm afraid.

I don't think the issue has anything to do with other applications on the server affecting the session lifetime. I can stay logged and navigate everything in LS fine, until I touch a survey. Immediately logged out.

So, I browse settings. I set up a user. I look at the updater (currently up-to-date). I look at themes. Whatever ..., for several minutes. I can view the list of surveys and still stay logged in. As soon as I've selected a survey and attempt to do anything more with it (like adding a question group), I get thrown out instantly.

Is there a way to enable and retrieve log files that may help identify what's going on? For uncaught PHP errors, my webserver adds an error log file in the directory of the file outputting the error, but I didn't notice such files (though I am not familiar with the codebase, so I may have omitted some directories).

You are using standard PHP sessions, right?
Or do you have database sessions configured in config.php?

As far as I know, standard PHP sessions. I haven't modified the config.php file - using things out of the box. The sessions stuff in that file is still commented out:

            // Uncomment the following line if you need table-based sessions
            // 'session' => array (
                    // 'class' => 'application.core.web.DbHttpSession',
                    // 'connectionID' => 'db',
                    // 'sessionTableName' => '{{sessions}}',
            // ),

@c_schmitz: How should a different application in the same webspace change the sessiontime of php?
If phpinfo inside LimeSurvey shows 1440 it is 1440. htaccess and other ways to change php-settings would be displayed via phpinfo.
The only external impact I can thing of is that the session path of php is tmp and tmp is cleaned/modifed by other applications.
That way session files crucial for LS can be deleted.

@ephemeralenergy
Who installed CentOS? Is e.g. SELinux configured or deactivated?

My website is hosted by fasthostst.co.uk - and I've had to dig a bit to try and find out about SELinux. (disclaimer: I'm rusty when it comes to Linux).

It looks like it's not even installed.

'sestatus' and 'getenforce' are not recognized as commands.

Using Putty to connect, so that shell may be limited. However, I find nothing in '/etc/sysconfig/selinux'.

@jelo In PHP the sessions are represented as files with a certain creation date/time in one directory. The same webspace usually uses the same directory to store all the session files, no matter what application.
If a different application on the same webspace shortens the session time it is very probable (not on every call but with a certain probability) that the session files older than that set session time are being discarded.
That's why it does not make sense to set session time in a PHP application (for the default PHP file-based sessions) because it will mess with other applications.

ephemeralenergy: Does it happen with every survey? Even with a very short 1-question survey?

I can't even create a simple survey :-/ Well, I can fill in the basics, name, etc., but when I try to add a question group, or anything else, I generally get booted out immediately.

Perhaps the best way to proceed is that I change the admin user and password and you can log in and experience it for yourself?

username: lsadmin
password: lsadminpassword

You'll see a survey there. Try to click it and, for example, go to "structure" to add a question group and try to preview. So far, I haven't managed to do even that.

Would help if I gave a URL too :)

https://www.ephemeralenergy.com/survey/index.php/admin/authentication/sa/login

Thanks for the testaccount.
LimeSurvey is reacting slow and logouts occuring from time to time.

To me this looks like a issue in the session storage concept.
PHP.ini is set to:
session.save_handler memcached memcached
session.save_path 10.10.111.52:11211,10.10.111.53:11211

Sessions are saved in the RAM, not file or database.
You should ask your provider to check the session handling.
I cannot sense a bug in LS at the moment.

Ok, I'll take it to fasthosts. Thank you :)

The implications of using cluster webhosting by fasthosts.co.uk are unclear.
Perhaps they have some issues with their platform. Perhaps there are some requirements, which applications have to fullfill.
How long do you use this account?

I've been with them for 2-3 years. And I've used limesurvey, wordpress and phpbb forum with them. Performance has never been their strong suit, especially when DBs have been involved, but I haven't experienced anything like this before.

See https://howto.biapy.com/en/debian-gnu-linux/servers/php/store-php-sessions-in-memcached
With memcached the session size is limited to 1MB.
That is useless for LimeSurvey as sessions are usually bigger than that.

This issue will be closed soon as it is obviously not a LimeSurvey bug.

To resolve this locally you could switch LimeSurvey to use database-base sessions.

Thank you, that did the trick - not getting booted out anymore :)

Just noticed another issue I need to investigate next. Some fields don't display (they flash for a moment and they're gone), like for question and help text (whilst the code field displays fine). Getting there.. :)