Getting null response during downloading certificate

Hello Azure Community,

We are using API Management for business transactions and supporting it with a Function App and Key Vault for security. We've updated our code to ensure the certificate is downloaded and remains in object memory for subsequent calls. However, we frequently encounter the issue below. Restarting the Function App temporarily resolves the problem for 1-2 hours before the cycle repeats.

Note: We have provided sufficient access to Key Vault and have opened a ticket with Microsoft. They suggested adding a retry option, which we implemented, but the issue persists.

Kindly suggest the solution as we are facing in Production and running out of ideas.

Error :

Postmethod error The implicit cast from Response<System.Security.Cryptography.X509Certificates.X509Certificate2> to System.Security.Cryptography.X509Certificates.X509Certificate2 failed because the Response<System.Security.Cryptography.X509Certificates.X509Certificate2> was null. (Parameter 'response')