Excel Spin Button only counts up then locks out.

Hi , The Excel Spin Button in the attaced sheet and in the second month only counts up then locks at max value. I note that the down button is inactive even when clicked but the up arrow will react and count up. The sheet is new so it has no information from another excel sheet. I have deleted the button and set it up again but I get the same error. Has anyone come across this.

Regards Moaman