Incomplete Hearts Missing from Map
I think it’s always been this way? You have to get near the heart for it to show up on the map otherwise it won’t appear there even tho the area was explored. I believe you are directed by the map UI arrow thing to a npc with a telescope who you talk to and he puts them on the map for you if you weren’t near them enough for t to trigger on the map.
Sorry I know that is confusing. Basically if you explore an area but don’t get close enough to the heart npc you will not see the heart. The best way to find it is by talking to the npc telescope guys or looking up the locations online.
Idk how long it’s been this way but my last map completion I had the same issue and that was about a year ago now.