Don't worry. I had the same problem.
The Heroku website will time out after 30 seconds. This is why you get the "application error" in your screenshot.
This is not a FOSSbot error really it's Heroku. Sometimes FOSSbot need more than 30 seconds.
The bot should still run and you can verify this on the "stats" page
Either way. If you are running the bot on an automatic schedule then this "application error" / timeout is nothing you need to worry about.
Try out the docker version if you have the time and then you won't even need Heroku.