Sony has announced a fix to an earlier file loss bug that impacted the a7R III and a7 III. This bug could cause the camera to stop functioning while writing data to a previously used card, resulting in the corruption of that image, and preventing the camera from playing back any images. Additionally, the new firmware addresses problems with a third party memory card failing to be recognized by the camera.
This bug was previously covered in the "Sony Warns of File Loss Bug on a7R III and a7 III" article, where a number of comments mentioned experiencing the issue. Fortunately, the bug seems to be relatively limited in scope, as users would only lose 1 image, or at worst, the burst of images, while the rest of the images on the card could be recovered.
I think Sony responded well to the issue, as the firmware fix was released relatively quickly, with the faulty firmware only available for 2 months. Of course, losing an image is never a good thing for photographers, but the actual circumstances to trigger the bug were addressable. Steps including formatting the card in camera, and disabling auto review of images all helped mitigate the issue.
If you are currently using V2.0 firmware on the a7R III and a7 III, it is recommended you upgrade to the V2.1 firmware. Users that haven't upgraded to V2.0 can now upgrade directly to V2.1, bypassing the problematic update.