Enderman spawn eggs in the form of an item entity or in an item frame will cause the chunk its in to regenerate when upgrading from 1.12.2. Enderman spawn eggs in containers such as chests are not affected. Other spawn eggs also do not cause this issue.
This issue is not world specific, but a world from 1.12.2 is provided: MC-132242.zip
Partially omitted due to length
[0630/195720:INFO:GameCallbacks.cpp(188)] game/com.mojang.datafixers.DataFixerUpper (Server thread) error Something went wrong upgrading!
java.lang.IllegalStateException: Named type name doesn't match: expected: block_name, got: block_state
[0630/195720:INFO:GameCallbacks.cpp(188)] game/bmt (Server thread) error Chunk file at 15,14 is missing level data, skipping