@a returns UUID of player

When targeting a player using @a in a command other than /kill, /say, /effect, /spreadplayers, /testfor or /tp, it will target something like be77f43a-203f-4d7f-8a87... instead of the actual player. When adding scoreboard values, it will display be77f43a-203f-4d7f-8a87... on the sidebar (the current display) instead of the player name. I tried a workaround of @e[type=Player] but that does the same thing. But @p and @r work. When typing the command, the output is "That player cannot be found".