seems like a frustration of Musical Mode popping on and of at will in existing projects and overdose of plugins on the master.
watch the orange musical mode leds per track and their assigned tempo in the audiopool
remove EVERYTHING from your master and make sure your soundcard inputs are not feeding back into your, or you don’t have an earlier export somewhere hidden deep away in a foldertrack playing along nicely, phasing away and driving your levels nuts, you wouldn’t be the first one who imported a mixdown export by accident. 