Hi I have the same on my 1DsIII, nothing I do is “mission critical” so I have decided to wait until it quits and assess new shutter vs EF-Rxx.
I find it shows up more on shots above 1/250th than it does on longer exposures, I guess the shorter the exposure the larger percentage effect the bouncing shutter has.
Expect the problem to show up on landscape shots soon at some point.
Cheers , Graham.