The Mongo Shell (not mongosh) produces structured log entries using --verbose that contain invalid JSON:
{ "t": { "$date": "2021-09-09T09:46:35.891Z" }, "s": "D1", "c": "-", "id": 23074, "ctx": "main", "msg": "User assertion", "attr": { "error": "DNSHostNotFound: Failed to look up service "xxxx-0.xxx.mongodb.net": Success", "file": "src/mongo/util/dns_query_posix-impl.h", "line": 324 } }
Note that the error is in the attr.error field where the quotes around the hostname are not escaped. The issue appears to be here.