MCP 9.35 rc1 names
The bug
The rendering rotation for shulkers are set in the net.minecraft.entity.monster.EntityShulker.onInitialSpawn(DifficultyInstance, IEntityLivingData) method. This means that shulkers with at least one NBT tag are not rendered correctly in spawners.
How to reproduce
/give @p spawner{BlockEntityTag:{SpawnData:{id:"minecraft:shulker",AnyNbtTag:0},Delay:12000s}}