When reloading the world, UUIDs on the scoreboard get cut off on reloading the world, making them useless.

How to reproduce:
summon ArmorStand x y z

scoreboard objectives add test dummy
scoreboard players set 1-2-3-4-5 test 200
scoreboard objective setdisplay sidebar test
==RELOAD WORLD
testfor @e[score_test_min=200]

You can see the entity 1-2-3-4-5 is no longer linked with the scoreboard. The scoreboard now looks for a player with name:
00000001-0002-00
Which can never be an entity.