The door drops fast on one side, or it won't come up past a foot before jamming crooked in the track - that's a cable, not a spring, and on the older stock common in Berwyn it's usually the cable that's been rubbing against a rusted drum edge for longer than anyone noticed. A fully snapped cable drops the door hard and leaves it sitting unevenly, often with the bottom corner canted down on the side that failed. A fraying cable, caught before it snaps, tends to show up as a jerky, uneven motion right before the door reaches full open or full close.
Don't force the opener past a jam - that's how a bent track gets added to a cable job. Households across this area number over a quarter million, and cable failure on original 1938-to-1950s-era hardware is one of the more common calls we get from this stretch, mostly because the parts weren't built to last eighty-plus years, and nobody expected them to.