Can't restore: DTLS certificate file not specified

When I want to restore a backup (same version), I get this error:

Extracting Backup
Extracting backup...
Processing certman
Resetting certman module data
Dropping table certman_mapping...Done
Dropping table certman_csrs...Done
Dropping table certman_certs...Done
Dropping table certman_cas...Done
Updating tables certman_mapping, certman_csrs, certman_certs, certman_cas...Done
No Certificates exist
Generating default CA...Done!
Generating default certificate...Done!
Generating CSS...Done
Restoring from certman [FreePBX\modules\Certman\Restore]
default already exists!
DTLS certificate file not specified on line 955 of file /var/www/html/admin/modules/certman/Certman.class.php
#0 /var/www/html/admin/modules/certman/Restore.php(44): FreePBX\modules\Certman->addDTLSOptions('9010', Array)
#1 /var/www/html/admin/modules/certman/Restore.php(27): FreePBX\modules\Certman\Restore->processConfigs(Array)
#2 /var/www/html/admin/modules/backup/Handlers/Restore/Common.php(133): FreePBX\modules\Certman\Restore->runRestore()
#3 /var/www/html/admin/modules/backup/Handlers/Restore/Common.php(121): FreePBX\modules\Backup\Handlers\Restore\Common->runRestore(Object(FreePBX\modules\Certman\Restore))
#4 /var/www/html/admin/modules/backup/Handlers/Restore/Multiple.php(52): FreePBX\modules\Backup\Handlers\Restore\Common->processModule('certman', '15.0.21')
#5 /var/www/html/admin/modules/backup/Console/Backup.class.php(286): FreePBX\modules\Backup\Handlers\Restore\Multiple->process()
#6 /var/www/html/admin/libraries/Composer/vendor/symfony/console/Command/Command.php(255): FreePBX\Console\Command\Backup->execute(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#7 /var/www/html/admin/libraries/Composer/vendor/symfony/console/Application.php(960): Symfony\Component\Console\Command\Command->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#8 /var/www/html/admin/libraries/Composer/vendor/symfony/console/Application.php(255): Symfony\Component\Console\Application->doRunCommand(Object(FreePBX\Console\Command\Backup), Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#9 /var/www/html/admin/libraries/Composer/vendor/symfony/console/Application.php(148): Symfony\Component\Console\Application->doRun(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#10 /var/lib/asterisk/bin/fwconsole(163): Symfony\Component\Console\Application->run()
#11 {main}