Well your darts look ok to me from the inside really. In a garment sometimes ironing open the seam allowance on a dart helps but with fleece or even fur you can't really do that. What you can do is kind of work the seam with fingers... man how can I explain this.

For me it is the tip of the dart that sometimes bumps or bubbles and if you work your fingers up and down the seam it can often soften it. Don't forget that also that pulling the fabric tight over your foam base and then picking out the seams should help also.