Weird Artifacts in Exported Audio

for some reason, there are these low drones that aren't in any part of the music playing at random times through the exported audio. I've had this problem a few times, only ever with this instrumentation.

best place to see it is in mvmt III at N and end of mvmt III going into mvmt IV.

this happens with all file formats.

***i can't attach anything other than the .mscz file because the file is too big.