I seem to think this happens to me on other sites as well so it might be a larger problem but anyway;
sometimes, when I'm on a thread, (not on the main page) and I'm logged out, when I log in from there, instead of putting me right where I was, I get sent to the previous thread I was on. So I always must navigate back to where I was, this is annoying.
This issue also happens to me. I'm not sure exactly how to reproduce it though.