I accidentally found the problem that wither the boss shoots his head on the target as "when he is drunk", when he is in the water.
Steps to reproduce:
Make a cage for a wither (like in the video I sent) and cage him
Make a target (preferably straight in the direction) Then let the wither shoot in the "dry" cage. (He will shoot straight)
Put the water next to him and watch him shoot off target (Like in the attachment)
Observed Results:
Wither in the water shooting off his target
Expected Results:
Water at the tail of the wither should not affect the trajectory of the wither heads
I have attached the world where this error happened here: https://www.uschovna.cz/zasilka/QAIM4R4AJ9J7N9NL-FY7/
Thanks, krampi
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In addition to what @unknown requested, you can also provide a copy of the world which will help in reproducing the bug.

Steps:
1-Make a cage for a wither (like in the video I sent) and cage him
2-Make a target (preferably straight in the direction) Then let the wither shoot in the "dry" cage. (He will shoot straight)
3-Put the water next to him and watch him shoot off target (Like in the attachment)
Observed Results:
Wither in the water shooting off his target
Expected Results:
Water at the tail of the wither should not affect the trajectory of the wither heads
I have attached the world where this error happened (Here: https://www.uschovna.cz/zasilka/QAIM4R4AJ9J7N9NL-FY7/ )

@unknown Edit the description of this issue to include the steps, observed results and expected results from your comment.
Thank you for your report!
We're tracking this issue in MC-80142, so this ticket is being resolved and linked as a duplicate.
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Some more insight: the Wither's rotation is changed when you place down the water bucket (since it is standing in flowing water). Therefore the skulls' direction become different as well, but because of MC-80142 they glitch when flying.
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