npm run push fails sometimes

There is some problem with the subtree command, sometimes even if the remote branch is older than the local branch the push won't happen.

Error log:

error: failed to push some refs to 'https://github.com/geekodour/gitpushblog.git'
hint: Updates were rejected because a pushed branch tip is behind its remote
hint: counterpart. Check out this branch and integrate the remote changes
hint: (e.g. 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.
child_process.js:526
    throw err;
    ^
Error: Command failed: git subtree push --prefix dist origin gh-pages
To https://github.com/geekodour/gitpushblog.git
 ! [rejected]        59691beac925775782ef2268ed4bd4f3e6d7c09e -> gh-pages (non-fast-forward)
error: failed to push some refs to 'https://github.com/geekodour/gitpushblog.git'
hint: Updates were rejected because a pushed branch tip is behind its remote
hint: counterpart. Check out this branch and integrate the remote changes
hint: (e.g. 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.