Edit cells using userform - not working after cell range is changed

With this code, the cell contents can be edited using a userform. Editing is by typing.
The cell range can be changed while the userform is active and editing is still possible, except for the problem explained:

When more cells are selected compared to the original selection, editing cannot be done for all cells.
For example, if 2 cells are originally selected, and then the selection is changed to 3 cells (while the form is still active), then the third cell cannot be modified.
The procedure is explained in the workbook attached.

Is there any way to fix this?

Thanks, I was battling with this one, would never have gotten it.
The above works as intended.
Cheers.