C4C Code list restriction error

Hello Expert,

During our operation on C4C, we encountered some issue with Code list restriction. A user with the role Manger is supposed to see no value from the dropdwnlist of the field Status if the status is Acquistion as it has been restricted. You can see below:

Everything was working fine until one day. With the same Aqusition status, a Mananger user deleted the text in the dropdownlist typing area and then the whole list of value of the Status field appears for selection. I think loosing the text value in this area cause the code list restriction to stop working as the is no value to match with the rule. You can see below:

Could you please advice what should I do to stop this behaviour of the dropdownlist?

Thank you very much.