As I already said, we don’t even know by now what the cause for your issue was. And there are actions that are recorded in the history docker and others that are not, like activating the mirror-axis. But only the actions that are recorded are revertible via undo, what is not noted there is not reversible, it is/was a destructive action if you want to call it like that in opposite to the possible non-destructive editing that is also possible.
Additionally, you lose all possibilities to undo when you save your file to disk or in the case Krita crashes.
Michelist