I agree to a certain extent with @cottonm4. What you are seeing is ghosting of the clearcoat due to different rates of expansion and contraction between the inserts and the playfield. Removing all of the inserts and regluing them prior to repainting does greatly reduce the chances of this occurring but may not totally eliminate it. What kind of bulbs do you have under the inserts? Incandescent bulbs give off way more heat than leds. I have found that incandescent bulbs under the inserts of restored playfields have a higher likelihood of insert edge ghosting than leds. For this reason, I have taken to using only led lights under the inserts of my restorations regardless of the era of the machine.

The most bomb proof method of repair would probably be to remove the inserts (if possible without damaging the inserts or the nearby paint work), reglue them, touch up the paint and reclear. I feel this is more work/expense than this playfield is worth and is risky due to the difficulty of removing the inserts now that they are buried under additional layers of clear.

If it were me, I would just live with it as is. If you are really intent on fixing it, I would shoot for a middle ground approach: sand the clear to give it tooth, touch up the keyline separations and reclear it (and switch the under playfield illumination to led if you haven't already).