A maximum of 10000 writes are allowed in a single batch operation.
In saying so, for your use case, where you are trying to bulk insert 500 documents, ideally should not cause issues.
However, to help me understand further, could you share a few details for the deployment:
The deployment architecture(stand alone, replica set, sharded cluster)
The command that you are trying to execute.
How large is the a single document size.
Are you able to efficiently do it without using crossref using shell command.
Can you share the explain plan for the operation?
In addition, since we do not have the expertise in crossref, I would suggest to reach out the CrossRef community page for additional information if the issue persists at their end.