Could be bent plates.
Could also be a loose jockey wheel back there, or simply a maladjusted RD.
I noticed that you've depicted an Ultegra shifter. Was this a recent upgrade? If so, and you are running an older drivetrain (6 sp, 7 sp...maybe with 8 speed) it could be that the chain is too wide for the chain jockey.
Also check it for "gunk".
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Good night...and good luck