Unable to close ticket created through Service Catalogue

I have just finished populating the Service Catalog, i have gone through the testing period to see whether it all works as it should and unfortunately it does not.

I have a 'pick list' which i have created in the 'Additional Fields' section of the Service Catalog so it is available to all of the template forms i create (see below).

When attempting to close the ticket it shows the below although the field CIA Incident Type is filled in.

Does anyone have any idea as to what i can do to sort this please? It appears to be a bug from what i can see, i have tried making the 'pick list' mandatory and not mandatory as well as have it left blank in the template as well as having it set with the 'Availability' field.

I am really stuck on this and its stopping us from rolling out this new form of raising tickets to the ServiceDesk so would appreciate some help ASAP.

Thanks,
Matt