Weird artifacting during playback and export

I'm having this issue as well. It's only become a problem since converting mono files to stereo in the multitrack, and it tends to only affect one (I typically have between 4-10 tracks like this). In one session, it'll be a random track that does this exactly how you describe it: it sounds fine as a stereo clip for a few seconds, but then the space suddenly expands, or pans from one side to the other, and it does this throughout the whole clip. It's honestly a gamble to wonder which clip it decides to happen to. And when clips are affected and it also exports in this way (stereo fluctuation at different times to the playback in Audition), it's unusable.  

No, I'm talking about the sound device that's either internal to your computer,or is an external usb device, that actually creates the sound. If it's internal it will be the device that feeds your headphone or output socket.

Do you mean like what I'm listening through? I'm getting the issue using multiple output devices. Tried it on my speakers and my headphones. And I don't get these issues when listening to anything else.

What sound device are you using? Even with some really 'good' devices I get the occasional playback glitch. Whatever you are using, it's worth checking to see if there's an updated driver for it.