Requester name not found

Requester name not found

Hello!

When we create a new ticket and begin type requester name the choices appear below if it's already in the database. But when I select an existing item the other form field will be empty and when I save the ticket the form warn me that "requester name is not in database" and offer to save it. 

How should we solve this issue?

Thanks in advance.
Sandor Ujhelyi