Example for setting automerge fails (with only one of my repositories)

[mvz]

I've been using the automerge example for a long time, but with my latest repository, created from a template repository that also uses this mechanism, the automerge fails with the following error:

GraphQL: Pull request User is not allowed to push to this repository (enablePullRequestAutoMerge)

I have tried updating my automerge action to match the current example and it now looks like this (note that I don't have an if in the second step since I currently want all dependabot pull requests auto-merged):

name: Dependabot auto-merge
"on": pull_request

permissions:
  contents: write
  pull-requests: write

jobs:
  dependabot:
    runs-on: ubuntu-latest
    if: github.event.pull_request.user.login == 'dependabot[bot]'
    steps:
      - name: Dependabot metadata
        id: dependabot-metadata
        uses: dependabot/fetch-metadata@v2
      - name: Enable auto-merge for Dependabot PRs
        run: gh pr merge --auto --merge "${{github.event.pull_request.html_url}}"
        env:
          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}

As far as I can tell, permissions on this repository are the same as the other ones. Any hints on how to debug this are appreciated.

[mvz]

If I re-run the job using the Web interface, it succeeds.