frtime applications consume high CPU even after closing/stopping the app

[gregid]

I was playing with frtime demos inside DrRacket and noticed that everytime I run any frtime code the CPU usage is high even after stopping/closing the app window. To stop it you need to close the DrRacket/kill the process. After reopening DrRacket CPU usage is back to normal. The behavior confirmed on Windows (by me) and Mac by @pnwamk

Edit: garbage collection seems to be working non-stop after closing the app as well.