Mistakes like that stick with you for years. Bosses never let you live down the early screw-ups. Just shows how much we learned the hard way back then.

My old Singer 4411 would still pucker with a denim needle and longer stitches. I found the presser foot pressure was way too high for thick layers. Backing it off just a little, like a quarter turn, let the fabric feed without getting dragged. Also, I stopped pulling the denim through from the front and just guided it lightly from behind. The feed dogs do the work if you let them.

What's so weird about them?