Elder Guardian Thorn Texture Does Not Show For some reason

Had this bug when trying summon Elder Guardian using Command (/summon guardian.elder ~ ~ ~) When Elder Guardian Spawn, The Thorn-Like Texture is gone, and when I hit The EldGuardian, Suddenly The Thorn Appeared. I don't know this is bug or not.. But See my screenshot.. Of my game play (and sorry if this issue is "duplicate" or else..)