How to unfocus an unfocusable Combobox?

We have a comboboxstring in our inventory. Normally we can hit tab to close our inventory, but when changing the option of the combobox we can not hit tab till we click somewhere else.

The combobox has “Is Focusable” disabled.

Is there something I can do after the “On Selection Changed” function? I have tried using the “Set Focus” and “Set Keyboard Focus” to no avail.

How can I be able to hit tab after selecting an option in the combobox with out having to click anywhere?