As pictured, coil stop bracket had come loose. The cause: a screw had sheared off, and another had worked its way loose. We didn’t have the exact match for the screw (#8-32 3/8" pan head with a black finish), so I put in something close enough until the matching part arrives. I also carefully tightened both left and right coil brackets to minimize coil movement, as that can cause the kind of stresses that shear off screws.