I had an inbox notification telling me of a comment reply on Portuguese Language Meta. I had not yet logged into Portuguese.SE or its meta on that particular browser instance. When I clicked on the notification, I got redirected to https://portuguese.stackexchange.com/. The second time I clicked the notification, I correctly got redirected to Write titles in two languages or not?.
After experimenting a bit with a throwaway browser profile (I only tried Chrome 43.0.2357.130), here's a general way to reproduce:
- Log in to one Stack Exchange site (e.g. Meta.SE).
- Type or follow a link to a private beta (e.g. Como usar corretamente "por que, por quê, porque ou porquê"?) or its meta (e.g. https://portuguese.meta.stackexchange.com/) on which you already have an account, but you haven't yet logged in on this browser instance.
- You get logged in, but redirected to the home page of the main site instead of the intended page on the main or meta site.
This is still happening as of December 2016 (IoT private beta), and I'm not the only one experiencing it.