SDErrorDomain error 104

Hello Klaus Blume,

Welcome to Apple Support Communities!

We want to help resolve the error you're seeing with the SSD.

Have you tried using Disk Utility to see if any errors are found? This can help check for issues and repair them as needed. Use the steps on this Apple Support page: How to repair a Mac disk with Disk Utility - Apple Support

"Repair volumes, then containers, then disks

For each disk that you're repairing, start by selecting the last volume on that disk, then click the First Aid button  or tab.

Click Run to begin checking the selected volume for errors.

• If there is no Run button, click the Repair Disk button instead.
• If the button is dimmed and you can't click it, skip this step for the disk, container, or volume you selected.
• If you're asked for a password to unlock the disk, enter your administrator password.

After Disk Utility is done checking the volume, select the next item above it in the sidebar, then run First Aid again. Keep moving up the list, running First Aid for each volume on the disk, then each container on the disk, then finally the disk itself."

We hope this helps to quickly resolve the error you're seeing during startup.

Cheers!