Re: Scrollbars ?

[Richard Stallman]

    (a) clicking (and holding) the handle moves the window contents one line
    down,

    (b) optional: when dragging the handle there are display quirks,

    (c) releasing the handle moves the handle up.

Are you using a mouse button which ought to drag the handle?  If so, I
think we see two bugs here.  (a) is a bug and (c) is a bug.

If you can develop a precise test case, and report it in a single
self-contained message to emacs-devel, someone will debug it.