All the mob spawners doesn't contain the mob they spawn inside the block, were they should be spinning, as early version. The spawn stills produces fire when active. I don't know if this is a problem that someone else has.
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He’s talking about the animation in the spawner block, not the function of spawning mobs. This issue is being tracked at MCPE-56879.
Are you in peaceful mode? If so switch to a different difficulty.