The bug

Upon unlocking a trade for an explorer map by leveling up a cartographer villager, the server is able to freeze while searching for the next ocean monument or woodland mansion.

To reproduce

1. Create a new world
2. Spawn in a villager
3. Place a cartography table
4. Trade with the villager
5. The server might freeze while the villager is leveling up

This is easier to reproduce in custom buffet worlds.

Original description

If I level up the cartographer villager beyond apprentice all entities freeze , also one trade is missing (the map which has the monument , mostly because I don't have any monuments in my buffet world )
If i start a regular world and go to trade with a cartographer the missing trade appears