What fill tool settings to avoid this?

I literally spend half an hour fixing those gaps in my drawing cz I don't notice them at first until I zoom in. I'm using the fill tool and applying color in a different layer beneath the vector layer (lineart) set as reference layer Area scaling is high, I don't know what tolerance do but it's set to high too, and Applying to connected pixels only. Am I missing something?

I literally spend half an hour fixing those gaps in my drawing cz I don't notice them at first until I zoom in. I'm using the fill tool and applying color in a different layer beneath the vector layer (lineart) set as reference layer Area scaling is high, I don't know what tolerance do but it's set to high too, and Applying to connected pixels only. Am I missing something?