[UPDATE: 12.18.18 Sony Firmware Update 2.10 for a7 III & a7R III and Firmware Update 4.10 for a9 provide a fix for this issue.]
Several readers alerted me to incompatibility problems with SanDisk 64GB Extreme PRO UHS-I SDXC & SanDisk 128GB Extreme PRO UHS-I SDXC memory cards in Sony a7 III, a7R III & a9 card slot 1 resulting in this warning: “Unable to read memory card. Reinsert memory card. Slot 1”
I’m told that OLDER SanDisk 64GB & 128GB Extreme PRO UHS-I cards work fine. This only appears to be a problem with NEWER cards – so the issue may be limited to recent production. As always, be certain to only purchase memory cards from a reputable authorized dealer to avoid counterfeits.
Reported bad batch numbers thus far include:
128 GB Sandisk Extreme Pro UHS-I – batch 766G
64 GB Sandisk Extreme Pro UHS-I – batch 838G, 839Z
• This is only an issue with Card Slot 1.
• In-camera card formatting does not resolve the issue.
• I have not received any complaints about 32GB Extreme PRO SDHC memory cards.
• A comparably-priced alternative is Sony SF-UZ Series UHS-I SD Memory Cards: 32GB, 64GB, 128GB, 256GB
• There are also no issues with:
Sony SF-G UHS-II SD Memory Cards: 32GB, 64GB, 128GB
Sony SF-G Series UHS-II Tough SD Memory Cards: 32GB, 64GB, 128GB
Sony M Series UHS-II SD Memory Cards: 32GB, 64GB, 128GB
SanDisk Extreme PRO UHS-II SD Memory Cards: 32GB, 64GB, 128GB