Initial merged branch from main creates chore PR, subsequent branches off main merged to main do not.

#### TLDR;
https://youtu.be/-xkt2RKCaEQ - 2:43
or
Created two branches off of the main branch, both with commit messages following the conventional commit convention, both with changes different from the other. Merging the first will create a chore PR, the second will not.

https://github.com/jaysonpotter/github-actions-tests - fresh repo that demonstrates the issue.

#### Environment details

- Programming language: NA
- OS: NA
- Language runtime version: NA
- Package version: 4

#### Steps to reproduce

1. Create a new repo containing a package.json and .gitgub/workflows/release-please.yml config.
2. Check "Allow GitHub Actions to create and approve pull requests" in Settings > Actions > General > Workflow permissions
3. Create a branch off of default branch (main, master, etc); Update-1
4. Create a branch off of default branch (main, master, etc); Update-2
5. Add a change to Update-1. In my demo I add an index.html
6. Add a change to Update-2. In my demo I add a README.md
7. Create PR to merge Update-2 to default branch.
8. Merge Update-2 to default branch.
9. Go to Actions and see release-please run and create a chore PR.
10. Go to Pull requests and merge chore PR.
11. Create PR to merge Update-1 to default branch.
12. Merge Update-1 to default branch.
13. Go to Actions and view the details of the release-please workflow and you'll see that the Update-1 PR "commit could not be parsed" and no chore PR is generated.

#### release-please.yml
```yml
on:
push:
branches:
- main

permissions:
contents: write
pull-requests: write

name: release-please

jobs:
release-please:
runs-on: ubuntu-latest
steps:
- uses: googleapis/release-please-action@v4
with:
release-type: node
```

Feel free to see any details in the repo I created to demonstrate this issue at https://github.com/jaysonpotter/github-actions-tests

Thank you for your time and help!

Start by reproducing the sequence in the linked github-actions-tests repository using .github/workflows/release-please.yml and the release-please-action@v4 workflow. Then trace how the action parses the two merged pull requests and their conventional commit messages. Done means the later branch is parsed consistently and produces the expected chore PR.

Written by the indexing model from the issue text.