I have had it happen twice, loss of bars, without out provocation. I do not buy any, so I acquire them by doing well on game. It makes it that more frustrating when I look up and I have 15, then its 4 or 5. This has happened before and I emailed about this to the website email.
So I'd love to know what's going on. I've played this game steady, and in 2 years, this is my first encounter and its causing resentment toward the game I love.