On figured woods I stop sanding around 180 till I get the first finish treatment on. Much finer and you hide all that beautiful "pop". I'm not quite clear on which sanding marks are causing the issue. In your first post you state that you cannot get the sanding marks out; OK, I'm good with that. In your second post you say that you are making sure that before changing grits, you have a consistent scratch pattern laid down with "no underlying larger marks" being left from the previous grit; here's where I get confused.
I think you are saying that you are getting machine marks from the 320 that you are finishing up with via the ROS, yes? If this is it, and you want to go to 320 before starting to finish (I go even finer sometimes for specific reasons) Once you have a consistent 320 pattern, set the ROS aside. Put a quality 320 grit paper on a decent sized flat block (2-1/4" x 9" or there-a-bouts) and sand with the grain. This should convert all your swirl marks to directional marks without having to remove too much more material. If you haven't yet, you can wipe with mineral spirits and cross-light the surface to look for any unwanted survivors.
At 320, in a light hardwood like maple, your swirl marks should be very near undetectable unless you are going dark on the colorant. You may want to look at some reviews on ROS, check you pad, change paper more frequently, etc. You mention pressing too hard. I don't press any harder than it takes to keep the sander controlled. Let the abrasive do the work. Otherwise you end up with inconsistent results . . . or I do anyway
. I use a $50-$60 Bosch that won the pattern battles. Great price for a great little sander so, of course, they discontinued it