I’d be surprised if it was actually a problem within the SDFat library.
I would recommend trying to just call the SDFat classes and functions directly from your main file, but in the way you want, just to make sure there isn’t somehow an issue with the way you are calling / handling the additional class abstraction. Then if that works, revisit the way you are structuring and using your Cryo_MicroSD class.
If you post some of the code where you are using the class in your main program perhaps we can see if anything sticks out there too.