Zombie Villagers have their "CanPickUpLoot" NBT tag changed to 1b when converted to Villagers, of course. However, the issue unfolds if the same Villager gets converted back into a Zombie Villager. They will then receive a new, random "CanPickUpLoot" tag. Instead of converting back to the old one. I'm not sure if this is intended, but it doesn't make sense that the "same" entity (keeps some data such as "CustomName" i.e) should change that tag when converted.
Thank you for your report!
However, this issue is a Duplicate of MC-88967.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – 📖 Game Wiki