I made a report on area effect clouds a few months back and when I went to check it still happened in 15w51b (it does) I noticed the shulker starts z-fighting with the falling sand, this never previously happened and yes I know that I could make the shulker invisible but that's beside the point.
Use this command to reproduce
/summon AreaEffectCloud ~ ~1.125 ~ {Radius:0.5f,Duration:2147483647,Effects:[],Particle:"take",Tags:["Block","BlockController"],Passengers:[{id:"Shulker",Invulnerable:1,NoAI:1,Tags:["Block"]},{id:"FallingSand",Block:"minecraft:stone",Time:1,Tags:["Block"]}]}
I'm not exactly sure what you mean. I pasted the exact same command to a command block and the shulker didn't fight anything. If you don't want the falling sand block to dissapear, you have to constantly set Time to 1 ( /entitydata @e[type=FallingSand,tag=Block] {Time:1b} )