At the top of the download pages for Sony’s a7 III and a7R III firmware, an update read:
IMPORTANT: We apologize for the inconvenience, but the release of this software update has been delayed. We are working on the issue and will release the update as soon as possible. (Added on 12-07-2018)
In an announcement post on the Sony UK website, Sony explains the firmware has been pulled due to two issues:
1. In rare cases, your α7R III or α7 III model may stop functioning while writing RAW data onto an SD card that has already been used multiple times.
2. With the α7R III, taking a picture while using the Auto Review function may occasionally cause the camera to stop responding.
The announcement says Sony ‘will provide updated system software addressing the above issues in mid-December.’ Until then, Sony is asking users of its a7 III and a7R III mirrorless cameras to back up all data currently on memory cards (or to use an entirely new memory card) and to ensure the Auto Review function is turned off when taking pictures.
Update (December 8th, 2018 at 4:34 EST): This article was updated with more information surrounding the reason behind Sony pulling the firmware and an estimated timeframe of when the new firmware update will be available.