When using commands such as "/testfor @e[score_objectiveName_min=3]" all non-player entities will be ignored. For example, if a player has a score of 3 on objectiveName and a pig also has a score of 3, the /testfor command will find the player but not the pig. This also applies to other commands such as "/tp @p @e[score_objectiveName_min=3,c=-1]".

This problem can be replicated by starting a new world and typing these commands:

/scoreboard objectives add objectiveName dummy

/scoreboard objectives setdisplay sidebar objectiveName
(This just shows what entities have a score in that objective; it's not part of the bug.)

/summon Pig

/scoreboard players set @e[type=Pig] objectiveName 3
(The pig's UUID should show up in the sidebar with a score of 3, proving it has been set.)

/testfor @e[score_objectiveName_min=3]
(There should be no output if the bug happens.)

/scoreboard players set @p objectiveName 3
(Sets your own score to 3, your name should appear in the sidebar.)

/testfor @e[score_objectiveName_min=3]
(This time the command will find you, but still not the pig. This bug also happens with all other entities besides pigs.)