Same issue here: it's more frequent if I try to use the normal dropdown on the Office page, but even if I use the bookmarks from the Main WIS page with the team ID in them, about a third of the time I end up on the team I was trying to switch from anyway.
I've tried clearing my cache and cookies, that didn't seem to make any difference (and probably wouldn't unless they just made some significant change to HD ... which is really unlikely).