I don't usually do birds in flight, but on a recent trip to the coast I took at least 100 shots of seagulls with the R7 and RF 100-400mm (no extender, though). A lot of the birds were out of the frame, but very few were blurry. This one is straight out of the camera with no cropping or post-processing. I also regularly use an EF 70-200mm f/2.8 L with the Canon RF adapter, and the results are uniformly good. I like my R6 more than the R7, but have no complaints about either one. I hope Canon resolves the complaint to your satisfaction!
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