Radio does not "stop" on M3+KF

On Flounder 6.0.1 running on the M3+Kingfisher, the radio and alg-service-radio work properly for most functions.  However, the service verbs "start" and "stop" do not work properly.  The "play/pause" button on the GUI calls these verbus, which turn into 4a mute/unmute on the radio role, which ends up at the smixer with verb="m3kf#radio_stream" with data {"mute":true} (or false).

There, the smixer fails, with the "function not implemented" errors shown below.

Nov 06 17:29:33 m3ulcb afbd-agl-service-radio@6.0[4308]: INFO: [API radio] Muted
Nov 06 17:29:33 m3ulcb afbd-agl-service-radio@6.0[4308]: [/usr/src/debug/agl-service-radio/1.0+gitAUTOINC+28f17bb63e-r0/git/binding/radio_impl_kingfisher.c:360,kf_start]
Nov 06 17:29:33 m3ulcb afbd-agl-service-audio-4a@1.0-14cc9c6[4275]: NOTICE: [API smixer] CtlSubscribeEventCB:hw:3 numid=1 name=pause-radio_stream pause=0 ret -38 [/usr/src/debug/4a-softmixer/0.1+gitAUTOINC+b678f39644-r0/git/plugins/alsa/alsa-core-ctl.c:554,CtlSu
Nov 06 17:29:33 m3ulcb afbd-agl-service-audio-4a@1.0-14cc9c6[4275]: NOTICE: [API smixer] CtlSubscribeEventCB error Function not implemented [/usr/src/debug/4a-softmixer/0.1+gitAUTOINC+b678f39644-r0/git/plugins/alsa/alsa-core-ctl.c:556,CtlSubscribeEventCB]
Nov 06 17:29:33 m3ulcb afbd-agl-service-radio@6.0[4308]: INFO: [API radio] UnMuted
Nov 06 17:29:33 m3ulcb afbd-agl-service-radio@6.0[4308]: [/usr/src/debug/agl-service-radio/1.0+gitAUTOINC+28f17bb63e-r0/git/binding/radio_impl_kingfisher.c:389,kf_stop]
Nov 06 17:29:33 m3ulcb afbd-agl-service-audio-4a@1.0-14cc9c6[4275]: NOTICE: [API smixer] CtlSubscribeEventCB:hw:3 numid=1 name=pause-radio_stream pause=1 ret -38 [/usr/src/debug/4a-softmixer/0.1+gitAUTOINC+b678f39644-r0/git/plugins/alsa/alsa-core-ctl.c:554,CtlSu
Nov 06 17:29:33 m3ulcb afbd-agl-service-audio-4a@1.0-14cc9c6[4275]: NOTICE: [API smixer] CtlSubscribeEventCB error Function not implemented [/usr/src/debug/4a-softmixer/0.1+gitAUTOINC+b678f39644-r0/git/plugins/alsa/alsa-core-ctl.c:556,CtlSubscribeEventCB]