I left town for a few weeks, but kept the desktop running, including many open terminals -- MATE-terminal v 1.24.1. Upon return, I found that left-mouse-button select (highlight-select, for cut-n-paste) stopped working ... for mate-terminal only!
Highlight-select works great in the the web browser, it works in xterm, it works in gnome-terminal. Just not in mate-terminal. (In other words, this shows that mouse kernel dev drivers and X11 seems to be working fine.) The time-stamps on
/usr/bin/mate-terminal show that it was not updated while I was away... so I am stumped.