Each asynchronous function started, starts in separate thread.
So in that example you will have 2 threads since 2 asynchronous functions
will be started, each with its own (different) script.
@nydigov Easiest way to fix this is to delete "Close Browser" action. If you don't have any open/close browser actions BAS will handle browser lifetime automatically.
If you want to handle it by yourself, add Open browser action before using any action which needs browser.