I've been testing the betas and going back and forth reporting issues with the SD card. In my case at least I'm pretty sure it isn't an OS level issue.
I worked this out by completing a series of troubleshooting steps:
- Cleaning the SD card slot
- Looking for an actuator switch in the slot that tells the OS a card is present (which can seize up). Pressing is several times with a cocktail stick can release it. Note: this switch only appears in earlier SD card slots on Macs and not in my 2.2ghz Macbook Pro.
- Blowing compressed air into the slot.
- PRAM/NVRAM reset.
- SMC reset.
- I tried a range of sleep settings, including disabling hibernate.
After the last step I considered that I must have a hardware failure, but instead I tried the following:
- Booting into safe mode and then testing the SD card slot.
- I found that with certain kernel extensions disabled, the SD card worked normally.
- To test further, I downloaded the latest OS installer and then installed High Sierra on an external drive.
- I found I didn't have the issue when using this drive!
I discovered that there is a flaw in the current version of the Jetdrivetoolbox software (used for ejecting SD cards made by Transcend before system sleep) that seemed to push the card reader off the hardware profiler after the machine wakes up. Note: the SD card should appear in the card reader and USB bus sections. After I uninstalled Jetdrivetoolbox, my SD card is working perfectly and behaves as expected. The only advantage of the software was that it allowed the system to hibernate (usually a Mac can't do this with an SD card present in the slot).
You may discover that it's a hardware issue or merely dust - or you have incompatible extensions or startup items that are interfering. Another option (I don't know for sure) is that using an installer to do a clean install on an external drive rather than using the recovery partition may force firmware updates to be applied. I also had an iPad charging issue (cycling between mount, charge and unmount) which was resolved installing the OS on an external drive that could be explained in this way...
