Zombie villagers have a short detection radius. They can only see you from like 12 blocks away when zombies can see you from up to 40 blocks away. Same for all other mobs zombies are hostile towards.
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Dr.Awesome4333
migrated
Thanks for the report
We are already tracking this issue on MCPE-50207.
Please feel free to add any new information you have there.
This issue has been linked as a duplicate of MCPE-50207.