What is one challenge with using vendor-specific headers in application maps?

Using vendor-specific headers in application maps can present challenges primarily because these headers may not be recognized by all intermediaries involved in network communication. Intermediaries such as proxies, load balancers, or API gateways may not have the capability to interpret or handle these headers properly, which could lead to issues in the routing or processing of requests. This lack of understanding can result in dropped packets or miscommunication between services, ultimately impacting the reliability and efficiency of the application's performance. Therefore, the challenge highlights the importance of ensuring compatibility and consistency across different components in a system.