I think ferrite beads are generally to stop emissions (Lenz effect?), and I doubt they would cause such a regular periodic result as displayed here. Still, you never know!
CCD fault, or dirt, or similar would still be my preference for this type of noise. When I push my levels close together (up at the white end), I get a grubby bed. Though, I can see one or two periodic bars (we're looking at different things I suppose):
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