Chrome Version: 71.0.3562.0
OS: Mac, Win, CrOS
MR: 7118.924.0.0

What steps will reproduce the problem?
Enable Harmony and Mirroring service with the following flag:
--enable-features=ViewsCastDialog,AudioServiceAudioStreams,NetworkService,MirroringServic

(1) Cast a tab to Chromecast device "A".
(2) From the same tab, open the dialog and select Chromecast device "B" to switch the device being cast to.

What is the expected result? The session on device "A" should tear down. Receiver should return to home screen. The dialog should reflect that casting on device "A" is stopped, and device "B" is now active.

What happens instead? Casting doesn't terminate on device "A", it just freezes (after some time, the brain freeze screen appears then returns to home screen). The MR dialog UI shows device "A" is still active.

Note that casting is successful on device "B".