Troubleshooting SIP call transfers and redirects requires the ability to identify and isolate the source of the problem, such as network issues, configuration errors, compatibility issues, or security issues. To help with this process, you can use SIP tools to capture and analyze the SIP messages and media packets for any errors, warnings, or anomalies in the headers, bodies, or payloads. Additionally, you should use the SIP trace or debug commands on your SIP devices or applications to check the logs for any errors or messages related to the transfers or redirects. Furthermore, you should compare the expected and actual SIP call flows to identify where a deviation or failure occurs. Moreover, you should check the network connectivity and quality between the SIP entities for any packet loss, delay, jitter, or congestion that may affect the transfers or redirects. Lastly, you should also check the configuration and settings of your SIP devices or applications to make sure they are compatible and compliant with the SIP standards and protocols. Lastly, it's important to check the security and authentication of your SIP devices or applications to make sure they are not blocked or compromised by firewalls, NATs, or malicious attacks.