This is a UX issue since it disrupts workflows.
When a site gets switched over to https, clicking the browser's back button will continuously redirect to the https page instead of allowing the user to navigate back.
Common scenario:
- Type something into search engine
- Pick a link to navigate to
- Site redirects to https site
- Realize you want to go back to the search engine's results and click back
- Navigates to the HTTP site instead and get redirected to HTTPS site
The only solution I've found to this is clicking and holding the back button down to get the drop down of previous pages to select from.