Template variables not saving even though it says 'saved'

Using version 2.7.1 and I am getting intermittent instances in various sites where template variables are not saving. When I click save, it get a message saying the document was successfully saved. But when I visit the document again, the changes made to the TVs are not there. This seems to particularly affect TVs where the input option is set to Image.

Any help would be appreciated as this is causing lots of issues.

The most common cause of intermittent saving problems is mod_security.

It could also be an issue with media-source permissions.

Another issue that has affected TV saving in the past is a mismatch in the MODX date_timezone System Setting and the related settings for the server and PHP.