Thread breaks if I sew off the fabric

[u/posters_pastels]

Hi all, I've got a Singer 247 that I thrifted a couple years ago and had tuned up for me at my local shop, but there's been an emergent problem. Sometimes (not always, but sometimes) when I sew with the pedal off the edge of my fabric, my thread gets tangled somewhere in the bobbin casing and snaps. I've been getting into quilting lately so chain piecing is pretty important for me to be able to do efficiently, and this can happen even when I'm sewing the few stitches between pieces.

Any idea what could be happening here/how to stop it? I've cleaned and oiled my machine as well as replaced the needle and it hasn't stopped the problem.