If trying to transport a villager through a portal or if you break a minecart with a villager in it in the portal, both appear to transport through the portal, but they do not arrive in the nether or if doing so in the nether, do not appear in the over world.
To recreate, push a villager in a mine cart into the portal, then break the mine cart.
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Thank you for your report.
However, your ticket has been resolved as a duplicate.
This issue has been linked to the original bugreport: MC-83350. You can find or add further information on that report.
Please search before reporting any bugs, as it's likely that one exists already.