VESQL database restore to Always On Availability Groups with automatic seeding enabled is hanging

Challenge

VESQL database restore to Always ON Availability Group with automatic seeding enabled (SQL 2016 SP1 and later) does not work. Veeam SQL Explorer log shows repeating records like:

10/23/2017 8:19:22 PM   11 (5160) SQL query: ALTER DATABASE [<database-name>] SET HADR AVAILABILITY GROUP = [<group-name>]
10/23/2017 8:19:32 PM   11 (5160)     Adding database to Availability Group '<group-name>'...
10/23/2017 8:19:32 PM   11 (5160) SQL query: ALTER DATABASE [<database-name>] SET HADR AVAILABILITY GROUP = [<group-name>]
10/23/2017 8:19:42 PM   11 (5160)     Adding database to Availability Group '<group-name>'...
10/23/2017 8:19:42 PM   11 (5160) SQL query: ALTER DATABASE [<database-name>] SET HADR AVAILABILITY GROUP = [<group-name>]
10/23/2017 8:19:52 PM   11 (5160)     Adding database to Availability Group '<group-name>'...
 

Cause

Restore to Always ON Availability Group with automatic seeding is not supported by current version of Veeam.

Solution

Manually stop automatic seeding prior to performing restore as described here.