Incorrect /testfor and /summon minecraft:wool output

In 2 command blocks:
/setblock -305 16 -1144 minecraft:glass
/setblock -305 16 -1144 minecraft:wool 11 (blue wool)
Block spawned: red wool
Also:
in other command block:
/setblock -305 16 -1144 minecraft:wool 14 (red wool)
Block spawned: glass

This odd block spawning occurs at random. At current time (8:46PM GMT+8) this is the mixup.
/summon also seems to have this problem.