Another user has somewhat recently reported a similar issue to you i.e. tracks with volume automation/modulation applied to them desynchronize when subject to virtualization - does this sound like the same behaviour you’re experiencing? Mixing different loops/tracks to "compose" a soundtrack at runtime in a Unity game
A desync when virtualization occurs shouldn’t be happening. Could I get you to upload your FMOD Studio project (or a stripped down version where you can still reproduce the issues) to your FMOD user profile so that I can take a closer look? Note that you’ll have to register a project with us to do so.