Hi Ivy, I'm sorry it took us a while to get back to you!
Can you please tell us which lessons this problem comes up -- is there a specific English/Chinese lesson where there is always a playback error like this?
Kindly send us a Diagnostic Report so we may troubleshoot immediately. For instructions on how to create a report, please see:
http://support.brillkids.com/index.php/article/ls-how-to-create-diagnostic-report