In 4.1, the taskbar places all of the tasks flush
against eachother and the edges of the panel. This is
contrary to how the gtk2 theme selected should behave.
Backdating to 3.18, I see it displaying correctly, so
something was changed to 4.1 which caused this problem.
It's working fine still but does not look pleasing, IMO.
Have had another user confirm this behavior.