So I am creating a model in blender 2.8 from this tutorial https://youtu.be/wdsY4BtlcpQ (in 2.7) and I just got to the part where he adds a multiresolution modifier to the model. When he adds the subdivisions, his model is smooth but mine has little bumps and a crease around the waist. (Picture 1)
When I subdivide further these bumps are more pronounced. After experimenting it looks like these vertices around this one loop are not moving at all when subdividing as if they're locked into place. I found this out by moving one of these vertices in edit mode (Picture 2) which changed the model drastically while other vertices would change the model only a little. (picture 3)
I already deleted the vertices and recreated them and that is why most of the waist is gone because this is my second time recreating the waist. Already checked for doubled vertices.
I also noticed this, when looking in xray mode there is a yellow outline that goes through this exact line of problematic vertices. (Picture 4)
Please let me know what I'm missing here. Really need some help with this one. Thank you.