I’ve been working on a song, and it pops during playback in the project.
It has always done this but the pops go away after I have used the mixdown function.
For some reason this one song is popping after mixdown.
What’s happening 
?
If the pops are actually in the audio material, then exporting will not get rid of them. If the pops are random they’re ASIO glitches which are not supposed to happen during export.
Good advice. I would also try using the ASIO slider to increase latency next time you record. It could possibly expose whether or not this is the problem.
I hope you’re not using that stupid Duplex driver. 