CoreStorageFamily::unlockVEKs() failed to unwrap the vek, status = e00002bc
I noticed fsck_hfs running when i get this error.

So i suspect that the volume needed to be fsck'd, and because this sometimes can take longer than the time the authentication is supposed to take, an error got signalled by the authentication dialog, leading to the e00002bc error in the system log.

A look at /var/log/fsck_hfs.log will tell you if this is what happened in your case.

On my 4T external disk the fsck took about 5 hours.