I would agree with you, but since disabling the feature my devices have
all showed up all the time and casting to multiple devices
simultaneously has worked every time. Maybe its possible that both the
router and google software were trying to accomp...
I solved my problem by going into router settings and disabling a couple
multicast options there, if you have a dlink router try that. Now all
speakers work together in a group or individually as expected. Check
your router settings!