I came across a minor peculiarity in Pd 0.49-1 running on macOS 10.14.2
I have created a multi-output device in my Audio MIDI Setup. It’s works a splitter where the audio is sent in parallel to the built-in output and to soundflower. I have named it ‘Built-in Output and Soundflower’.
In Pd I can select it as output device in the menu but after pressing OK it takes and stores the 'Built-in Output' as device instead of my ‘Built-in Output and Soundflower’. If I name the multi-output device differently (i.e. ‘Multi out’) I can select it properly and everything works as expected. It seems that Pd only looks at/remembers the first x characters of the name of the selected device.
Best!