RaptorBravo

I work as a seamstress for a handbag designer and I am having problems with wavy zippers. I use tape to affix the leather to the zipper and sew, careful to not push or pull the leather as I go. I have tried sewing on paper as an attempt to stabilize but am still having a problem. I sew on an old consew industrial that is serviced regularly. See pictures for an example of what I am talking about. Any help would be much appreciated

Hello! I’m having an issue when sewing leather with the wrong sides together. The picture is the bobbin side of the sewing. I’m not sure what my problem is exactly. Is it my bobbin tension? Or pressure foot pressure? Any insight would be much appreciated. I tried adjusting both but saw no difference.