Sometimes, more or less often, git fetch command executed by quickbuild fails with the following error message/response:
> 2018-07-12 09:43:48 - Failed to run command: git fetch --all --tags -q
> Command return code: 1
> Command error output: fatal: git fetch-pack: expected ACK/NAK, got 'A ref was requested that is no longer valid. The ref may have been updated while the git-upload-pack request was received. Please try again.'
> fatal: The remote end hung up unexpectedly
> error: Could not fetch origin
This is caused by the nature of the http(s) request used by git and modifications during these, which occurs more likely with increased action on a repository.
Quickbuild should follow the advice in the response and retry the fetch command automatically to avoid failures during CHECK_BUILD_CONDITION.
Basically this would make sense for every git command. If there is a "Please try again" contained in the message it really should try the command again.