If you click on e.g. Pre Sale Questions, you get into this category. If you are in the category and click on page 2, you will get back into all categories ... you will not be in the category "Pre Sale Questions".

Just to flesh out the above (which might be better submitted as a bug via support, but as it affects this site too then all good)......reproduction steps:

1. Go to forum homepage
2. Change to fluid view
3. Click on the forum name for a topic - result: fluid view is filtered to show only items in that forum.
4. Go to page 2 - result: fluid view now shows all topics from all forums again....filter is lost, even though still selected in the right-hand sidebar.