StreetDeck sometimes can allow multiple instances to come up. This is fixed in 220.127.116.11 and the cause of your COM port and restarting issues. You can disable the tray app by renaming SDTrayApp.exe to something else.
For now just hit stop and play and your radio should work after resuming. This is fixed in 18.104.22.168.
Fader and balance controls were also added in 22.214.171.124.