My new uPOG motorboats.....is this normal?

[juse]

Got a micro POG for Christmas, thanks to my 6 year old 

I like it, but after playing on it for about 45 minutes, it started to motorboat with the octave down dimed. Prior to that it didn't. Now it does it all the time. It is pretty loud sometimes.

Is this normal? Do I need to swap it for another one, or do they all do this?

I wonder because it didn't do it when I first started using it.