If you click anything in the sidebar and continue to hold the mouse button while moving the mouse, the sidebar hides, preventing successful completion of the action. To reproduce, open Bookmarks in the sidebar and try to move one of the bookmarks to another location in the list by dragging and dropping. The sidebar will disappear once you start moving the mouse and uc-autohide-sidebar-delay expires.
If you click anything in the sidebar and continue to hold the mouse button while moving the mouse, the sidebar hides, preventing successful completion of the action. To reproduce, open Bookmarks in the sidebar and try to move one of the bookmarks to another location in the list by dragging and dropping. The sidebar will disappear once you start moving the mouse and uc-autohide-sidebar-delay expires.