SD Card randomly ejected after sleep

I have exactly the same issue with my MacBook Pro (Retina, 15-inch, Mid 2015) with a 256Gb Transcend JetDrive. There is no cable that connects the drive to the MacBook as its plugged directly into the onboard SDCard reader.

This appears to be a common issue after upgrading to Monterey as I see other posts when googling on this issue. One of the suggested fixes is to install the Jetdrive Toolbox and enabling Power Save mode which according to the manual "Power Save helps you save power by automatically ejecting your JetDrive Lite before the Mac enters Standby mode and remounting it when the Mac wakes up"

I've installed it and enabled Power Save, we'll see if that fixes the issue.

Greetings Ben______,

Thanks for reaching out to the Apple Support Communities! It sounds like you have an issue with your SD card ejecting when you wake your Mac from sleep. If you run First Aid on the disks, does First Aid point out any errors? Does running First Aid resolve the issue? Learn how to do that here: Repair a storage device in Disk Utility on Mac

If the issue persists, does changing the cables that connects your drives to your Mac help? Are you connecting directly to your Mac or through a hub?

Make it a great day!

There is an issue with SD cards and Monterey. SD cards are not readable if inserted before booting up but are if inserted after the fact. I'm guessing that when your Mac sleeps and then wakes up it is a similar issue. Perhaps Apple will address at next update.