TDE flickers wildly and unusably; KDE OK

I just installed TDE on a new-to-me system running debian stable (buster). All the initial system installation was done from a live CD, and it installed KDE. That installed version of KDE works as well as KDE ever works these days. In particular, though, the screen looks fine (1920x1200) and everything works as expected. In the newly-installed TDE, though, the desktop flickers wildly and the desktop is simply unusable: input is lost during the flickers, so most keyboard/mouse input is not even seen by the desktop. Where should I look to try to eliminate all the flickering so that I can get a usable TDE? Doc -- Web: http://enginehousebooks.com/drevans