When we release a new version of the primary visualforce page of our Force.com site (or certain components), users on those pages get an Unauthorized/401 error.
This seems to only happen on pages where there is dynamic content being loaded into the VF page. In other words, when there are API calls being made without the page being reloaded.
For example, on our contact form, customers choose categories to describe their issue, then we suggest articles that might solve their issue. The articles are loaded dynamically without refreshing the page.
If we release a new version of the VF page template, all users currently on the contact form page will receive an error when they go to Submit the form (which inserts the case into Service Cloud via an Apex class).
How do we release new versions without giving users an error?