A good idea, if you are populating the clients into a Vue variable from an ajax call, is to use the vue tools plugin to see that actual data that's being populated into the variable, and make sure you are passing in the "id" as well as the "name".
Then when looping through the for each part of the combo-box, make sure you are assigning the value to the "id" field.
If you post the vue portion, I'd be happy to look further.