[CentOS] CentOS 7 MATE flakey mouse

I'm using the MATE desktop (via 'yum groupinstall "MATE Desktop"') on
CentOS 7.  I'm finding the mouse to be rather flakey in the sense
that:
  - in MATE Terminal, clicking on text and dragging the mouse (in order
    to highlight the text and copy it to the X cut & paste buffer) will
    sometimes drop the highlight (thus not copying anything), or
    stop and restart the highlight (thus copying the wrong text).

  - double clicking in MATE terminal to do highlight and copy in
    by-words mode often grabs the wrong text

In all other versions of xterm-like terminals since the dawn of time,
these kinds of operations have been rock-solid.  Now they're unpredictable.

Is anyone else seeing this kind of behavior?

Devin