If you do a forced push of a branch which has a PR the PR isn't updated. The branch view shows the new commit but in the PR no change is visible. If you decline and re-open the PR the change is visible.
Do you have any branch permissions setup that might be preventing a force-push?
Yes, using the Prevent -> Rewriting history setting probably something you want to keep set on master. Your original issue was the the pull request didn't update in your feature branch.
If you are still having an issue I recommend you open a bug report with the support team so they can investigate this further: https://support.atlassian.com/contact/#/