Not sure if this will help in your case as i did not experiece the ControlZ issues “undos”. The laggyness i felt on 5.1, slow menus, delayed saves etc seemed to clear up after a clean up.
https://forums.unrealengine.com/t/how-to-force-shader-recompile-of-everything-like-the-first-time-you-run-the-engine/1450/4?u=shawndageek