k1lsc0 downed by unknown reason and it could not be accessed via ssh.
Finally, I could recover without the Dolphin glitch and applied burt snapshot at 16:40 for all related models.

= What I did =
- Dolphin for k1lsc0 was disabled. (Dolphin for k1als0 was accidentally disabled at the same time.)
- k1lsc0 was reset from the BMC web interface.
- k1als0 was rebooted.
- Burt snapshots were applied for all related models.

Dolphin glitch can be avoid by using reset on the BMC web interface even when the SSH connection is not reachable.