The problem is probably due to soft paint...
If the UC and M205 are removing the defects, (and they should be), the light scratching could be coming back as you wipe the products off.
One thing I cover in all my classes and live broadcasts if you watch them, is as you work your way through the paint polishing process you need to continually bring up the level of your carefulness as well as bring up the quality level of your microfiber towels.
One thing that helps me to finish out mar free on softer paints is to finish out using a very light cleaner wax.
See what I wrote in post #23 here... How to prevent Micromarring while removing polishing residue