I just got a Lutron bridge (Pro), turned on telnet and added one of my pico audio remotes. Then using the Button Controller app started assigning the buttons. Whenever I try to assign button 3 and select the Control a music player, select a sonos device and set the volume to 50 it gives this error, then this error always displays after that clicking button 3 and I have to delete the button controller and start over. It did work to select a virtual switch for button 3 so maybe I can assign a virtual switch to set the volume and call that. I also tried setting this as both a "p" and "q" type remote and it errored out on both.
An unexpected error has occurred trying to load the app. Check Logs for more information.
Error: No signature of method: buttonController31.disp() is applicable for argument types: (java.lang.Long) values:  Possible solutions: dump(), is(java.lang.Object), grep(), find(), wait(long), with(groovy.lang.Closure)