When I see this, I feel that the gates are dull. The dull edges of the gate create the flakes at the runner is separated from the part. Part of your issue may be that the gate edges were dulled due to shear on the melt as the cavity is filled. The edge of the gate could be rolled over as well.
Making them sharper will fix the flaking but you’ll have to watch the initial melt filling the cavity and ejection speed. An air blow off with really clean compressed air might be the easiest thing to do.
Rick.