Start11 ver 2.51 Taskbar icons erratic when taskbar aligned top

When the taskbar is aligned at bottom, all is well.   When the taskbar is aligned top, the icons actions are erratic.  When the mouse hovers over the icon, actions differ depending on the specific location of the mouse.  Clicking on just the right spot will open the window, whereas other spots nothing happens.  I like the taskbar at the top, so this is a nuisance.  Appreciate fix.