Moving multiple characters at once works locally, not across the network
I was hosting the game and I was not the game master (but I don't think this matters). My druid had conjured several beasts, so I hit the "Add a PC" button, created one new character for the beasts and dragged it multiple times onto the map. Then I drew a rectangle around all of the beasts (or instances of the one beast if you prefer), which successfully selected them, and I moved them all on the map. On my map, all these characters were correctly moved together but all other participants in the session, including the game master, saw only one of the beasts move and the others stayed in place.