In draw mode, after performing one editing on a curved path, if you undo it, nothing changes.
After performing 2 edits on a curved path, if you perform the first undo it, it goes back to the state after the first edit. If you perform the second undo, it stays in the state after the first edit.
The same thing happens with a simple curve
After all the undos are done, there is nothing to save. It almost looks like the undone is made right internaly, but the redrawing of the scene doesn't happen? I don't know. Do you experience this as well?