I cannot add a 5th device to a group (for multi-room sound). Four devices works fine. The 5th device is greyed out. Clicking the "i" on the right displays "Check network connection." All devices are on the same network. If I take a device out of the group, then I can add the other device. So I can change the devices in the group, but not get all 5 in it. It appears that there's a max of 4 devices in a group but I cannot find that stated anywhere. Is there a way to get all 5 in the group?