@ James
Now I see…
Like I originally said, you should exclude the page from your page cache. You’re running the Endurance Page Cache plugin. So…
When you navigate to the directory you see the cached page (when not logged in, ie. the mobile devices). This cached page will be served by the page cache plugin until it expires (which appears to be weekly [or daily, depends on precise which version of .1 is installed on your site).
When you select a category, the page is not being served from the cache, when you change the drop down to display all, you are seeing the uncached page.
This is why you are not seeing the page change and why you see different results when choosing the show all category option.
There does not appear to be any options for this cache plugin so I installed Code Snippets and added a filter which should tell Endurance Page Cache not to cache the directory page.
Hope that helps!
