I know the hearts are repeatable and reset in each daily period. That’s not what this is about. The last couple of maps have been set so once you’ve done the hearts, they show as complete on your world map and your character’s map completion for the zone will stay at 100% even if you let them go empty again at reset and don’t redo them.
I have now completed Lake Doric on two alts over the past few days. I went back into the map this evening on the first alt to do some achieves and discovered that I was at 94% and that my Lake Doric map showed 4/6 hearts done.
I did two easy hearts (entry area and Loamstead). Each one ticked my completion up again, so doing just those two, leaving the other four empty, had me back at 100%. I am not sure if I did any hearts on the second alt this evening after reset, though I think I did not. Just tossing that in in case it’s a factor.
The main reason I bothered, as I am not really ocd about the percents if I know I did the map completion and got the reward, was to test if it would give me the completion reward again, in which case it would be an exploit needing more private and rapid reporting. Fortunately it did not give me another reward beyond seeing that nice “100%” again.
Here are the screens showing the erroneous completion amount (note the 6 empty hearts in the first one, and only 2 filled in for the third).