Scenario 15: A distributed system with resource servers across two data centers occasionally rejects valid, non-expired JWTs as 'expired' or 'not yet valid'.

This points to clock skew between servers — if the token-issuing Authorization Server's clock and a resource server's clock drift even a few seconds apart, strict exp/iat/nbf validation can incorrectly reject a technically-valid token. Fix by enabling NTP time synchronization across all servers and configuring a small, explicit clock-skew tolerance in the JWT validation library.