mix down errors when exporting

I am using the latest audacity version (2.2.1) and my laptop runs MacOS Sierra. I have been struggling with issues in mix down output from Audacity, with tracks being smashed together in the wrong places of the mix for reasons that I cannot understand. I have 12 tracks imported into Audacity and lined up after editing in a continuous mix. When I export Audacity spits out a single file, but the mix down is wrong. Instead than respecting the alignments that I selected while working into the program, the exported mix down file has clips of different tracks (anywhere from 10-20 secs) sprinkled and mixed all over the continuous mix and in places where they shouldn’t mix. It seems as if Audacity mixes things up, cutting and chopping small audio clips from the tracks imported and then dropping them randomly in parts of the mix, making the work unusable. I don’t seem to be able to figure out what the issue is. I deleted the version and downloaded another dmg (from the the audacity team.org site) and the issue still persists. Any help would be greatly appreciated.

You can get Audacity to produce a mix-down track without exporting a sound file.

Tracks > Mix > Mix and Render to a New Track.

(That location may be a little wonky)