Why is my Rocksmith score going down?

Noticed a couple of days ago the big arrow that shows your score escalation was actually going from the top to the bottom. I wondered if maybe the game maxed out at it's max score so I started watching my score. I swear yesterday it was 65 million, but today it's down to 61 million. What gives?

Update:

Now it's down to 59 million. Strange, it doesn't seem to go down after an event, but rather after I qualify for an event or rehearse / riff repeat a song.

Update:

Now down to 55 million.

Update

Now down to 40 million.

Update

Now down to 30 million.

Apparently there is a bug that caps your combined guitar and bass scores at 1 billion. Each will increase just fine until they sum to 1,000,000,000, at which point increasing one subtracts from the other. By reports, it sounds like the bass score won't decrease, only the guitar score.