couldn't unmount disk 69888
The error message "couldn't unmount disk 69888" usually occurs on a Mac computer when you try to eject or remove a disk, but the system cannot do so because it is still in use. The number 69888 refers to the disk identifier.
Here are some steps you can try to resolve the issue:
Close any applications that might be using the disk, including any windows or tabs that may be open.
Use the "lsof" command in the Terminal app to find out which processes are using the disk. Open the Terminal app, type "sudo lsof | grep /Volumes/diskname" (replace "diskname" with the name of your disk), and press Enter. This will show you a list of processes that are using the disk. You can then try quitting those processes or force-quitting them if necessary.
Try running the "diskutil unmountDisk force" command in the Terminal app. Open the Terminal app, type "diskutil unmountDisk force /dev/disk identifier" (replace "disk identifier" with the identifier of your disk, which is usually something like "disk1" or "disk2"), and press Enter. This will force the system to unmount the disk.
If none of the above steps work, try restarting your computer and then ejecting the disk again.
It's important to note that forcibly unmounting a disk can potentially cause data loss or other issues, so it's always a good idea to make sure that all applications and processes are closed before trying to eject a disk.