The company using the wrong port is the most likely root cause of why secure LDAP is not working. Secure LDAP is a protocol that provides secure communication between clients and servers using LDAP (Lightweight Directory Access Protocol), which is a protocol that allows querying and modifying directory services over TCP/IP. Secure LDAP uses SSL (Secure Sockets Layer) or TLS (Transport Layer Security) to encrypt LDAP traffic and prevent unauthorized disclosure or interception.

Although I might agree that OAuth 2.0 could be an answer as well, since it can help with rate limiting by accepting only authorized traffic, this is not as specific as it should be for the proposed scenario.
Bot protection is a security measure that helps prevent automated scraping activities by detecting and blocking malicious bots that attempt to access the APIs. This can help reduce the processor utilization on the APIs and prevent scraping activities from affecting the performance of the system.
Rate limiting is a security measure that limits the number of requests that can be made to an API within a given time period. By implementing rate limiting, the security engineer can help prevent scraping activities that may cause high processor utilization on the APIs.

It is important to keep track of the versions of open-source libraries that are being used, and to monitor the CVE website for any vulnerabilities that have been identified in those libraries. This can help the organization stay aware of potential security issues and take appropriate action to address them.
Performing unit testing of the open-source libraries is not necessary, as unit testing is typically focused on testing individual units of code within the software, not on external libraries that are being used.