Possibly a conflict error. Trying to skip possible conflict files.

Error: The process '/usr/bin/git' failed with exit code 128

Your repository allows merge commits and rebase merging. However, Backport only supports rebased and merged pull requests with a single commit and squashed and merged pull requests. Consider only allowing squash merging. See https://help.github.com/en/github/administering-a-repository/about-merge-methods-on-github for more information.