Have you tried any different window managers? You can try marco (no compositor), marco (compton) and compiz from the mate tweak. You can also install mutter and then choose it from the mate tweak. There is also a guide for openbox https://www.maketecheasier.com/replace-mate-window-manager-with-openbox/. Finally you can try xfwm4 Using xfwm4 (xfce's window manager) with Ubuntu-MATE.