I just checked again with a brand new wordpress install and twent-twelve installed and the same issue applies. Actually the page /events/upcoming doesnt even exist anymore, the only reason it was redirecting was because wordpress can’t find the page anymore. I also tried your suggestion of updating settings and permalinks.
It looks like with the new version you guys switched the default url for the events page from /events/upcoming to /events, which breaks any links going to the previous events page and messes up any seo efforts.
Can you guys please switch it back, or allow the option to switch it?