Steps to reproduce:

1. Create new spreadsheet
2. Enter 10, 20, 30 in the three first cells of the first column
3. Select these values and click Insert Chart
4. Select a reasonable sheet area for the chart and choose a default chart by
pressing Create on wizard's first page.
5. Right-click on the unoccupied area of the chart (for example, below the
legend) and select Chart Wall
6. Choose fill style "Color" and select any color (other than default one)
7. Close the dialog with OK
8. Try to undo it by pressing Ctrl+Z (it doesn't work)
9. Try to undo it by selecting Undo from Edit menu instead (it works this way)

You can undo the operation with Ctrl+Z too, but only if you click the chart area
first. Without clicking it, it works one way (Edit/Undo) but not the other
equivalent way (Ctrl+Z), so I think it's a bug.