If I understand correctly, you have a page that sometimes redirects to somewhere else and sometimes simply displays a content. If the page decides to redirect, dispatcher won't cache it. However, if the page displays a content (even once), it will be cached and from this moment all users will get the cached resource.
You can do 2 things:
- move the redirection logic to Javascript, so it'll executed even if the page is cached,
- add a cache rule to dispatcher configuration preventing this concrete path from being cached.