Bot errors if repo already has `all-contributors` branch

**UPDATE:** See https://github.com/all-contributors/app/issues/460#issuecomment-1545212342

**Describe the bug**
I have tried following all the instructions, but can't get the bot to work on a [specific repo](https://github.com/ClimateTown/knowledge-hub) (but works on all minimal example repos, and even a [fork](https://github.com/VeckoTheGecko/knowledge-hub) with `main` pointing to the same commit using the same call to the bot).

**To Reproduce**
I've tried, but I can't reproduce this...

Timeline of things I've tried:
- Updated README with below table section ([PR](https://github.com/ClimateTown/knowledge-hub/pull/84)) as in docs, and called the bot. Bot gave error message.

Added to README:
```
## ✨Contributors

Thanks go to these wonderful people ([emoji key](https://allcontributors.org/docs/en/emoji-key)):

This project follows the [all-contributors](https://allcontributors.org) specification. Contributions of any kind are welcome!
```

- Bunch of testing to see if I was calling it wrong, or if having no config was the issue ([all my bot calls failed](https://github.com/ClimateTown/knowledge-hub/pull/85)).
- Removed the config again for simplicity. Forked the repo and tried, and the fork worked. Both repos had `main` at the same commit. ([original repo bot call](https://github.com/ClimateTown/knowledge-hub/pull/85#issuecomment-1482806437), [bot call on fork](https://github.com/VeckoTheGecko/knowledge-hub/issues/1#issuecomment-1482809241))

**Expected behavior**
The bot to make a PR instead of replying with "We had trouble processing your request. Please try again later.".

**Additional comments**
Sorry this is such a weird issue with minimal debugging help from me. Let me know if I can be of any more help, Any ideas?? I'm out of ideas here 😢