Search box value vs. typed text

Hi I am having difficulty entering a new data using search box.

If the value is totally new, I can use search box’s typed text and it will add data to my thing/table.

However, if thee’s already the same value, it will show on dynamic choices. if I chose from the dynamic values, sometimes it doesn’t reads it, and return a blank value after I added it to the table…

So if a new entry, it can understand ‘typed text’, but for existing entry, it can understand search box’s value.

how do I solve this issue? I need the user to be able to use existing value if another user already added it, but also can add a new value, if no one has added it.