Hey @clottman,
I think there are a few confusing things here. The first is around your step 6:
Re-run the deploy preview for PR #1 - see the same failure as before, as if netlify.toml hasn’t been fixed in the production branch
If you use the retry deploy button in the UI, that will build the exact same commit that you pushed to create that specific Deploy Preview, even if there were changes to the production branch in the meantime. The PR is opened against a branch at a particular moment, and frozen at that commit. So you’re correct that you would need to rebase your PR branch against the production branch in order to pull in changes from the production branch.
Our deploy previews build what’s included in your PR- they don’t rebase against master before building. Does that help?