Problem viewing Thumbnails in classifieds

This is a weird problem but I can only view one thumbnail at a time. Then I have to close that window and re-click the next thumbnail and so on.
I used to be able to click on a thumbnail and then there would be arrows to scroll through all thumbnails in the thread.
I recently did an upgrade on My Macbook to the newest Firefox.

 

Amazingly, Right after I posted this, It started working again. At least for one classified ad.

 

Mystery solved, I had been using a zoomed view. Somehow zooming in disables the "scroll" through thumbnail feature.