A few months ago, I bought a 4 TB SanDisk Professional 4 TB Thunderbolt SSD. It worked fine. When my wife wanted a drive to use with Time Machine on her Mac, I gave it to her and bought another. I used it with Time Machine on my MacBook Pro M4. It seemed to work fine, but I never did a restore. Today, I was on a Zoom call with a friend and he said that his similar drive wouldn’t stay mounted on his Mac. I said mine works fine, then took a look at my desktop to verify that.
Oops, no drive icon.
I fired up the Disk Utility.
It sees the drive, but it’s not mounted.
I ran First Aid.
That failed.
I tried to erase and reformat the disk, but that failed, too.
I rebooted the machine. No luck.
I tried to delete the volume.
No joy.
Is this a hard failure? I’ll try to reformat the disk on a Windows machine.
SanDisk has a well documented recent track record of drive failures. You can read about the case action lawsuit here:
https://www.sgtlaw.com/cases/sandisk-extreme-solid-state-drive-defect-litigation
In the meantime stick to the T7 Shields or Crucial X9 Pro series.
@BFaini has a write-up on the drives and references the Sandisk issues:
https://www.fainimade.blog/2023/09/crucial-filling-void-left-by-sandisk.html