When the wither on bedrock does the dash attack in melee mode it destroys such a high volume of blocks that the game cannot handle it and basic tasks like switching inventory slots becomes almost impossible. It also becomes impossible to hit the wither meaning that the fight is not possible to win and will result in that area of the world not playable. 
2023111020365000-11B64E28AD7A49CA9EC8AC007BE858C6.mp4
https://1drv.ms/v/s!AvO8p_YZlCj0gjIwfq4xI1lqChbW?e=ocjE9O 
onedrive links for media that shows 30 second videos of the issue over time.