Minecraft 16w02a, Minecraft 16w03a, Minecraft 16w05b, Minecraft 16w06a, Minecraft 16w07a, Minecraft 1.9 Pre-Release 1
When executing the command "/playsound minecraft:entity.player.burp player @a", I get the response "This player cannot be found"
The command works fine with @p or if you use a real players name, but just not with @a
The same thing happens both when the command is executed by a player or is executed by a command block.
And it happens with every <source>, not just "player".