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

i´m doing curl request on web application (also on bash) , recogonized following behaviour:

sometimes i´m doing a

 curl --header "apikey: an1ceke3y" https://test.host.com/api/endpoint 

i following:

 curl: (60) ssl certificate problem: unable local issuer certificate 

but sometimes, second after fail request made successful request.

i made little test 6 requests:

1) success 2) error 3) success 4) success 5) success 6) error 

shouldn´t

unable local issuer certificate 

happens time? there way better debug issue?

additional informations:

api endpoint behind microsoft azure load balancer

success request ( -v )

* 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 ( -v )

* 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 local issuer certificate 

thanks!