Good work ! My experience was similar, although I have an RTL SDR dongle. Some observations. I started my first run from the Terminal rather than using "Run". There were several displays relating to the audio, which all read :
portaudio_sink: :work(): Error writing to audio device: Output underflowed
When I stopped the run, a message was displayed :
Gtk_Message: GtkDialog mapped without a transient parent. This is discouraged.
My first run was a test of receiving an FM stereo signal. I found that at an IF gain of 40 dB, that overloaded the system. I therefore reduced the IF gain to 20 dB, and FM reception and demodulation was much better. I therefore recommend other users should try reducing the IF gain from the maximum to around half-way, to ensure that they are not overloading things. This is normally what I have to do with this dongle, which has a maximum gain of 43, but works best at 19.
Yes, this is some excellent software, which is easy to set up and to run. Thank you and congratulations on all that has been achieved so far. Version 26 on RPI3 with the "Stretch" release is a success, as the previous poster reported.