I can apply multiple coupons when I shouldn't be able to

Hi,

I have unticked the box "Can this coupon be combined with other coupons?" but If I add a coupon to an order which is allowed to be used with other coupons then add more coupons (that are not allowed to be used with other coupons) I can then end up adding lots of coupons to an order

See attached screen shot

Only one of those coupon codes is suppose to be able to be used with other coupon codes

Kind Regards
Kieran