Hey everybody! I recently made my preschooler some flannel pjs; I used the overlock stitch on my sewing machine (I have a Brother XR-9000) and I did not adjust the stitch width or length from its automatic setting, which is a 2.5 length, 5.0 width. They’ve been washed and worn a couple times and although the side seams are holding up well, the arm holes have come apart in multiple spots on either side! Does anyone know what I’ve done wrong so I don’t make this same mistake again? I’m new to shirt sewing… Thank you so much!