When players are in lava and have their head under the surface of the lava, air bubbles appear and when there is no more air bubbles the player starts to take damage(drowning)
Attachment from silentwisperer's livestream of the error: https://clips.twitch.tv/MagnificentRelentlessBobaBatChest
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duplicates
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Thank you for your report!
We're tracking this issue in MCPE-17073, so this ticket is being resolved and linked as a duplicate.
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