Found the solution shortly after my last post.  Returned the entire package to place of purchase and no more problem.
New Inspiron 7700 which came with a Dell mouse KM636.  Mouse stops scrolling, won't continue until the mouse is moved horizontally.  No system issues found.  All software and drivers up to date.  Dell sent new mouse and it has the exact same issue.  Tried two different Logitech mice and one Microsoft mouse neither of which exhibit any problem.  Dell is now apparently stumped.  Anyone else seen this?
Dell mouse scrolling issue