The git connector use tests try to clone a github repo via ssh. This usually results in an authentication error because JSch doesn't have the ssh private key. This private key has to be assigned to a github account.
What's confusing is that the test sometimes pass magically, or aren't run at all.
The easy fix is to replace the ssh url with a http(s) one. I'm still wondering though why the tests passed sometimes in Eclipse, or weren't run at all.