I am seeing this bug again in the latest update, 1.16.20 I think it is. When phantoms first spawn, they attack once immediately. But after the first attack, they then go into permanent hover. They feign diving again, appearing to dive down a few blocks, but then pull out of the dive and go back to hovering again. I am seeing this on the Xbox One.
Thank you for your report!
We're actually already tracking this issue at MCPE-67244, so I will resolve and link this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
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