Playback glitching during recording Sonar X3e

Welcome to the forum Lin.
 
Five year old artists have so little patience.
 
What is most likely happening is that some other process o your computer is deciding to run and taking cycles from Sonar.  Common programs that cause this issue are Windows Update, backup programs, and other scheduled services that may be running on your computer.  This could also be your computer nodding off (sleep mode things) because of keyboard inactivity.  You may want to look at your Windows power settings.
 
If you have wireless networking, you may need to disable your network connection while recording.  Unlike wired networking where there are clear voltage levels to represent the Ons and Offs, the wireless card has to stop and wait while it listens.  This causes problems for time critical things like sound generation.
 
Another common issue is the recording clock getting out of sync.  In your Sonar Preferences, check to see that your audio interface (Scarlet) is showing under 'Driver Settings' as your 'Playback Timing Master' and your 'Recording Playback Master.'
 
Glen