That has been happening for a fair while. When you level up it starts the xp bar from 0 again, meaning you can only gain what it takes to level up.
I generally try to level up before playing a tourney seriously if I know I'm likely to lose points in that fashion.
What Joe said. Sometimes things like that can cost you a DT win so make sure if you are close to levelling up, do so before the DT.
Yes, I noticed this happened to me before, I was wondering why, and now I know, UR staff please try and address this problem ASAP as it can have a large affect on many people