Probably not a bug, but not something that made me happy!
I generally run with the 20% XP potion running on my TR'd FvS. I've been intending to lesser reincarnate him to fix some stat point allocation for a while, and this weekend I decided to plunk down the 895 or so TP to do that. Less than an hour prior, I had been running in a good XP group, and my XP boost ran out so I bought another XP potion and drank it. So, at the time I lesser TR'd, I had around 5 hours 15 minutes remaining on the buff.
I should have thought about this, and realized that the buff would go away... but of course, had I done that, I wouldn't be posting this!
Not a big deal, since the potions aren't that expensive, but still not very nice.