Second request failed (socket hang up)

I’m using a remote webservice to generate a token with a basic authentification.

When I send my request throught postman the first time it works, but whenever I try to send it again I get the following error “Error: socket hang up”.
If I close and restart postman it works again, but only one time.
If I juste wait for like 5 minutes it also works again.

I guess postman keep something alive with the server but I don’t now how to fix that.
I tried adding a “Connection: close” instead of the default “Connexion: keep-alive” but it does not fix the issue.

I searched the web for this issue but I did not find anyone with the issue except the one that proposed the header Connexion solution.

Here is the output of the console of three tests (the first one working).

Thanks,