A client site is running v5.7.5.13. Their Administrator users have a permissions problem whereby intermittently they can't access various parts of the UI when logged in. This is most prevalent when they go to use the 'Add Pages' and 'Dashboard' panels that slide in from the right hand side of the browser. They click either of the buttons in the Admin bar, the right hand panel opens and it says 'Access denied' instead of seeing the usual options. This is when they are on the front-end of the site only. If they are already in the dashboard, it doesn't seem to happen.

I am wondering if they possibly have split lines on their web traffic on their network, and perhaps the site is seeing requests coming from different IP's. I vaguely remember seeing something on the forums about this years ago with an older version of C5, but can't find it at the mo...

There is no additional Caching being used, apart from the standard C5 caching. It also only happens for them when they access it over their network. When I access it from my 'single line' it always works correctly, so I'm sure it is something about their network. I can't replicate and so can't troubleshoot. They are a large corporate, so I can't expect them to change their setup, or be a unique case.

Has anyone seen a similar thing occur, or maybe offer any advice?

Thanks!