Steps to reproduce:

1. Go around 5 directories deep from the home directory
2. Go back up 2 directories so the below directories are still in the bar
3. Resize the window such that when the window is focused, the home folder is hidden and when not focused, it is visible.  This will be when the end of the navigation bar is about a centimetre away from the search button.  You may have to tweak it a bit, the sweet spot is only a few pixels.
4. Hover over navigation bar

If you got it to just the right size, it should start shaking/jolting/oscillating/shifting back and forth between showing the home directory and hiding it.