What is causing clicks/pops in exports?

I've edited several song sessions. 100+ files. All of them make a click/popping noise at least once in the track. 

The click/pop is very loud. It sounds like a glitch/error. It ruins the track. 

Sometimes the spots of the clicks change. Meaning sometimes they export fine. Other times they happen on an entirely different location of the song. 

I've noticed I can fix some of them by declipping even if the vocal isn't clipping. Same with using a limiter. 

Is there a reason for these clicks/pops? The files aren't coming anywhere close to red/clipping.

But they sound like very tiny spikes of clipping. 

Are there solutions to this problem?