Next step would be to thread dump to get an idea off why the threads are being blocked.
There are a number of ways to thread dump. See https://www.baeldung.com/java-thread-dump
I’m usually using jstack.
So thread dumping will give you stacktraces for all current running threads and can give an indication on where the threads are being stuck. I would report a bug on the chromcast binding if you think that is the issue. Then you have to describe how you are using it and provide the threaddump as well.
One easy way to see if it is the chromecast binding is to remove the binding and rules and see if you still have the issue or not.
/S