abasham

I have been getting familiar with the Cub over the past few months and I have had some similar experience. I will share a little in the hope that it helps you as well. In my first week or so, I practiced to learn. I had similar outcomes where I would practice on scrap then sew at the same weight and have problems. My take-up spring broke within my first week and I spent some time adjusting the new one until I had a good balance. This worked for a while and I was seeing improvement. I again broke a spring a little later. In each case, getting the spring to the right place was a guess. When I put the next spring on, I marked the point that gave me the best result on the side of the machine. Since that point I have been able to adjust the machine to sew at different weights successfully. I learned that one of my problems was trying to sew leather that is too thin. The base weight for reliable stitches is 5-6 oz and even then it gets challenging to get the tension right. When I work on weights around 8oz and up to the machines max 3/4 inch it has very little problem. When changing height during a stitch (sewing over a seam or off of a high point) the presser foot has a tendency to not fully return to full pressure on the material. This can cause stitch slippage. I have learned to keep an eye on that as I'm sewing. I am no expert and I am just learning myself, but I would say that I am getting better with using the Cub and knowing how to set it up. It has a bit of an experience curve, but I was new to sewing with a machine anyway.