@OrderColumn applies as expected on the database layer but not on the managed entity upon save.

If a POST/PUT request needs to return the saved entity, then it's needed to clear the entity manager, and request the object from the database again.
e.g.

repository.save(theEntity);
entityManager.clear();
return repository.findById(theEntity.getId());

It should be sufficient to do just:

return repository.save(theEntity);

For example the @Version annotation works as expected.