It looks like you’re getting “fines” in your grind (i.e. bits of bean which are significantly smaller than the average size). That’s what causes this slightly sludge-y paste you’re seeing. If the coffee you’re making tastes fine to you then it’s nothing to worry about, but you might find that it tastes over-extracted (slightly bitter or acidic) due to the larger-than-intended surface area of the ground coffee.
You could try cleaning your grinder out, but you might find it’s hard to avoid without changing grinders entirely.
