PHP Sessions deleted after 2 or 3 minutes in MS Azure scale set environment

Question

I am having a problem with the deletion of php sessions after about 2 to 3 minutes in a Microsoft Azure scale set hosting environment.

The application is built using the php, Zend Framework 3. The app has been heavily tested and been through many rounds of QA with no problems. The testing was done on a single VM within MS Azure. However, when it is deployed in the production, scale set environment the session deletion issue occurs. In all other environments the sessions only expire after the configured time of 30 minutes, which is set from within the Zend app but also reflected in the php.ini settings. The app uses an external Redis server to store the session data as opposed to the default 'files' setting in PHP.

The hosting is Red Hat 7.6, Apache 2.56 with PHP 7.1.

I am not the devops, just the PHP developer, so I do not have access to the Azure environment and do not know how it is configured.

I am not sure if it is relevant to the php sessions issue but there are other odd behaviours that differ from other environments. For instance URLs that work correctly everywhere but in the scale set. Query strings causing the page to crash, trailing slashes causing assets to not be loaded and a couple of other quirks.

I don't expect anyone to diagnose this issue from the small amount of information I am able to provide but if anyone had suggestions of things that could be looked at I would be extremely grateful.

Many thanks.