Not even Undo History works at times…
Undo is not one the most stable things dpending on what you do, frequently saving is.
If you suspect your blender is corrupt, then simply download it again it isnt that large.
Cheers, good to know I am not the only one with this …
Read the manual to understand how undo works and its limitations https://www.blender.org/manual/interface/undo_and_redo.html?highlight=undo