AJAX back and forward on agile views renders funny things

Problem

If you go to a rapid board and navigate between some agile views (using the 1,2,3 keyboard shortcuts or similar), then you use the back and forward buttons in the browser (or <alt> + <left-arrow / right-arrow>), the header for the agile board is re-rendered, and an extra "collapse" button gets added to it.

These additional buttons purely add clutter to the page - the button continues to function as expected.

Work around

Refresh the page and the buttons will be removed.