pkg upgrade error after system failure

[Ilia Gorstkine]

Sony vaio pcg-41213v
5.6-release DragonFly v5.6.2.4.g39d387-RELEASE #4

When updating packages by pkg upgrade at the installation stage my laptop freezes tightly and I had to turn it off via the power button.
After booting the system, the pkg upgrade command throws errors:
Updating Avalon repository catalogue...
Certificate verification failed for /C=SE/O=AddTrust AB/OU=AddTrust External TTP Network/CN=AddTrust External CA Root
34371375740:error:14007086:SSL routines:CONNECT_CR_CERT:certificate verify failed:/usr/src/lib/libressl/../../crypto/libressl/ssl/ssl_clnt.c:1121:
pkg: https://mirror-master.dragonflybsd.org/dports/dragonfly:5.6:x86:64/LATEST/meta.txz: Authentication error...
...
pkg: https://mirror-master.dragonflybsd.org/dports/dragonfly:5.6:x86:64/LATEST/packagesite.txz: Authentication error
Unable to update repository Avalon
Error updating repositories!

I have tried other repositories, but with the same results.
I tried installing ca_root_nss, but pkg install ca_root_nss returned the same error. 
pkg fetch, pkg search, pkg update - same error.
pkg backup -r /var/backups.sql.xz - recovery went ok, but nothing changed.
pkg version returns the following:
pkg: sqlite error while executing ALTER TABLE packages ADD licenselogic INTEGER NOT NULL DEFAULT(1); in file pkgdb.c:2477: no such table: packages

Can anyone help restore pkg database?
Thanks in advance!
-- 
Ilia Gorstkine
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