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They go away but come back?
Usually a fist thought is that something is on there, and needs to be removed. But if they seem to disappear temporarily then I'd ask if it's actually the surface itself that is changed or damaged. Maybe you are temporarily getting it wet, making it seem to disappear, but then after a few days it dries and shows itself again?
I'd consider an "extra soft" toothbrush - thinking it's rigid enough to get into those grooves but not enough to scratch things further. And a variety of off-the-shelf cleaners (stay away from direct acetone or anything like brake cleaner). If it won't come off you might have to live with it. There's a risk you'll get rid of it eventually but have a bigger problem.
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