Time Capsule is suffering from insomnia. HDD don't spin down.

[Wal-demar]

Thank you for the great work.
My Time Capsule Gen 5 is suffering from insomnia. After installing SMB, everything works perfectly—except that the hard drive does not go into sleep mode.
I logged in via SSH and checked the /mnt/Flash/tcapsulesmb.conf file. The settings are correct:

TC_CONFIG_VERSION=2
TC_DEPLOY_RELEASE_TAG=v2.1.2
TC_DEPLOY_CLI_VERSION_CODE=20123
INTERNAL_SHARE_USE_DISK_ROOT=0
ANY_PROTOCOL=0
DISKD_USE_VOLUME_ATTEMPTS=2
ATA_IDLE_SECONDS=300
ATA_STANDBY=''
NBNS_ENABLED=1
SMBD_DEBUG_LOGGING=0
MDNS_DEBUG_LOGGING=0

The doctor only finds one problem: FAIL missing local tool smbclient. Surely that can't be the problem?
Edit: doctor checks passed. I deployed tag v2.1.3, but same problem
fsck doesn't find any errors either.
What else could this be?

[Wal-demar]

The problem was solved by installing tag 2.1.3 and then downgrading to 2.1.2.