Hi Lisa , I baked those rice snap biscuits and they turned out fine.  Kids loved dunking them in glass of milk.  I know when I was putting the mixture onto the oven tray with baking paper I made sure I spread out the mixture so it was not thick.  Also my oven was playing up so left them in for another 5 minutes.  I then let them cool ... and well they snapped alright .  :)   My kids are loving the shortbread !!    Hope this helps ?