I am up to the sword only portion of the wither fight and cannot proceed any further because the lag in the fight is so bad I get the wither effect before I can even see what is happening and die. Even getting within 50 block distance of the wither the lag is so bad the game becomes unplayable.
Thank you for your report!
We're actually already tracking this issue at MCPE-21854, so I will resolve and link this ticket as a duplicate.
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