To fix this, Ground.news should update their algorithm to perform much more scrutiny for headlines trending on right-leaning sites. Especially considering that nearly all their right-leaning sources have very low or basically non-existent factuality ratings.
...or just remove (entirely) any "news" source that doesn't have a high factuality rating. That would be the most logical choice but I do sympathize with the fact that would remove nearly all right-leaning "news" sites.
If I were in charge I'd reorient the leanings so that sources like NPR would not show up as "left-leaning" but as centrist (i.e. a more European alignment which is more historically accurate/real, IMHO). Which is where they actually sit (in reality). Sites like Breitbart would be discarded entirely as failing tests of factuality.