Either most Canon EOS R5 owners aren’t as observant as they like to think they are or this might not be as common an issue as some may believe. But at least one EOS R5 owner, who goes by the name juanmaasecas, has spotted what he believes is a bug with the in-body image stabilisation system in the Canon EOS R5.
He posted a video showing how the bug appears and has confirmed that others can reproduce it. Essentially, the issue is that the IBIS has a slight shift as the photo is being taken, causing it to become blurred. Subsequent images in a continuous sequence of shots show a stable, sharp clean image. But that first one always has blur, according to the video. At least one person commenting on the video reports that the same happens with his EOS R6.