"CTRL+Z" / "Undo" to get a time signature back makes KEY signature ineffective

Please click on the image to enlarge.

Steps to reproduce the bug.
1. Do a score like this.
2. Delete the last 2/4 time signature.
3. Delete the 4/4 time signature.
4. Hit "CTRL + Z" to have the 4/4 time signature back.
5. Change the layout.
6. Notice the key signature bug in measure 5.

As a workaround you can replace the key signature in measure 4 with the same key signature so to force the program to re-do things right.
EDIT:
However, there are situations (that I'm not currently able to reproduce) when this just doesn't work, and you first have to do some time signatures fixing. If of any help, I think it has something to do with:
* having the current meter different from the nominal one;
* having two equal time signatures one after another.