After 3.0.0 came out I tried the dual printing support and noticed that if you've selected an ooze shield addition it prints AFTER the first layer is complete. This means that the inactive extruder has the entire first layer to ooze all over the model. It should clearly print the ooze shield BEFORE it prints the actual model.
I emailed support and got no response whatsoever.
If you're a dual user and can confirm what I observed I recommend contacting support to ask that this be fixed.