Sonar X3 Fluctuations in Tempo

Hello all, First time poster, long time lurker.
 
I recently did a cover of the song Angel Witch by the band of the same name. While I was mixing it, I noticed that the tempo consistently fluctuates about 4bpm in certain sections of the song. The project has a few tempo changes in it, but when this issue occurs the tempo in the project says its still at a solid 192.
 
Later on, I started another project and noticed the same thing. Slight tempo fluctuations.
The metronome is set on audio sync. I don't think my interface has a clock source. I'm not sure if there is a more accurate setting for the metronome sync. Maybe my laptop is too crappy to keep a solid tempo?
 
The battery in my laptop recently went out. I don't know if that would be the cause or not since its still running on wall power.
 
Any ideas on a fix? Is it my laptop's battery?
 
Thanks

Thanks for your reply. It's possible I'm hearing things, but it drove my crazy to the point that I searched for a few hours on Google and finally decided to create this account just to ask. I first noticed it in the midi drum track by itself without the metronome on, listening to the ride and snare. Does the interface automatically use its own clock?

If there's any audio in the project, including soft synths and the audio metronome, SONAR will automatically set Preferences > Project > Clock to 'Audio', which is the interface's sample clock. One thing to double-check would be that the Playback and Record Timing Masters in Preferences > Audio > Driver Settings are set to channels of your Scarlett interface. but a problem there would not usually have the symptoms you describe.
 
Also, you should make sure the the Prepare Using Buffer under MIDI > Playback and Recording in Preferences is set to at least 500ms to prevent MIDI dropouts. But, again, this would not usually cause a tempo problem.
 
I kind of assumed the project has a mix of soft synths and recorded audio; is it all soft synths?
 
There have been issues issues in the past with soft synths going out of sync with audio tracks when looping without the metronome on. I think most of those were cured by the final release of X3, and it's usually clear that it's a sync problem not a fluctuating tempo.