Not email related, but might be related.
I've also noticed a change in behaviour recently. I always leave a section or thread open on the browser of my cell phone and if I (after a while) want to check for updated topics I simply tap 'back' which will force a refresh of the previous forum page that was loaded and next I can click the updated topics link.
This approach used to work 100% of the time but recently the behaviour changed. Recently tapping 'back' often but not always results in the forum navigation links not showing (as if one is not logged in). One or more 'back' is required or leaving the forum completely and next going there from scratch.