u/ZMajcherZEM

i am using a singer heavy duty sewing machine with heavy duty thread. i thought it was a tension problem as i am sewing with a denim, but even after several attempts of adjusting it, it still jams. i was able to get it work a few times after cleaning and rethreading, but now its jamming again. I saw other people on here with similar problems and they were told to pull the bobbin thread back; i made sure to pull the thread back but the problem still persists.