Success & Error: curl: (60) unable to get local issuer certificate - bash

Question

I´m doing some curl request on my web application (also on bash) and recogonized the following behaviour:
Sometimes i´m doing a
curl --header "ApiKey: an1ceke3y" https://test.host.com/api/endpoint
i get the following:
curl: (60) SSL certificate problem: unable to get local issuer certificate
But sometimes, even a second after the fail request i made an successful request.
I made a little test with 6 requests:
1) Success
2) Error
3) Success
4) Success
5) Success
6) Error
Shouldn´t the
unable to get local issuer certificate
Happens all the time?
Is there a way i could better debug the issue?
Additional informations:
API Endpoint is behind a microsoft azure load balancer
Success Request ( with -v )
* successfully set certificate verify locations:
* CAfile: none
CApath: /etc/ssl/certs
* SSLv3, TLS handshake, Client hello (1):
* SSLv3, TLS handshake, Server hello (2):
* SSLv3, TLS handshake, CERT (11):
* SSLv3, TLS handshake, Server key exchange (12):
* SSLv3, TLS handshake, Server finished (14):
* SSLv3, TLS handshake, Client key exchange (16):
* SSLv3, TLS change cipher, Client hello (1):
* SSLv3, TLS handshake, Finished (20):
* SSLv3, TLS change cipher, Client hello (1):
* SSLv3, TLS handshake, Finished (20):
Error Request ( with -v )
* successfully set certificate verify locations:
* CAfile: none
CApath: /etc/ssl/certs
* SSLv3, TLS handshake, Client hello (1):
* SSLv3, TLS handshake, Server hello (2):
* SSLv3, TLS handshake, CERT (11):
* SSLv3, TLS alert, Server hello (2):
* SSL certificate problem: unable to get local issuer certificate
Thanks!