I put a new UI mod in place yesterday that uses a square minimap and the like. Due to the way the button works and using /census to launch it anyway, I decided to disable the button.
So, when taking a census, it'd launch the UI and start a census. If I closed the UI, it would pause the census without the minimap button enabled so I put it back, resized the frame for it and set it to an area on the UI layout. Now it's back to working fine.
The change doesn't mess with my layout, I was just to lazy to rework positioning and the sizing issues of the minimap button before, but still, I found it rather interesting that it seemed to need an active/visible frame for the census to run.