Withers do not move down to follow the player when the wither's health is half or lower

    When I was playing on the snapshot 21w41a I ve made the wither and it was normal until he was half health ,he did not come near me i saw him coming only a bit but there were still like 10 blocks distance and i needed to fly to him which he keep going up and i was at a time at 1000 y

     i know that he wassent right but i did not try to just stay on the ground for longer then 5 min 

     this bug makes the wither fight way harder pls fix it