In this case, the first API call na_server_invoke is successful and we are able to create clone. That indicates there are no issues on the filer/target side but the subsequent calls for na_server_invoke like delete clone are failing.
One point to note is, we are using NMSDK in a shared libarary and OpenSSL version (1.0.2r) is statically linked to it.
What is your "s" object? Is it connection to cluster or cluster with tunneling to vserver as well? Ensure you have vserver tunneling setup because destroy only works with vserver context and not with cluster context. "Vol clone create" can with cluster context also.