I want to know why component must be shutdown and IllegalStateException occur in swing.

We are currently developing on-site using a swing-based library.
Press the search button (SearchBox), select an item, and return to the caller screen to set the selection value.
(I'm sorry that it's hard to understand the text because it's a little confidential information and it's hard to post screenshots and codes.)

For some reason, the exception "java.lang.IllegalStateException: component must be down" occurs.

I would like to first pursue the cause.
I would appreciate it if you could let me know what is possible.
I am also organizing the information that I can provide now, so I will add it.

The IllegalStateException itself is a non-check exception "indicating that the method was called at the wrong time", so let's check how to call the method as well.