In Thunar left pane if i have something mounted there can be a eject icon to the right.
If there is enough items in the list there is a scroll bar.
Scroll bar covers part of the icon (some times).
If i hover the cursor on the scroll bar it becomes wider. Covering more of the icon.
So i only have a few pixels area to click the icon.

...now for some reason the eject icon have move longer inwards so the scroll bar does not cover the icon.
But then when i click the icon a waiting icon appears to the left of the eject icon for 1 second and the eject icon is move right under the scrollbar.

I also tried adding an entry in /etc/fstab and when i did that i did not get the eject icon.

So it seems inconsistent where and when the icon appears.