External_storage: notify Call to undefined method

hi,
i need some help with External_storage. Try to use “external_storage: notify” but it stops working after 20 minutes.
(version: 21.0.0.18)

thx!

sudo -u www-data php -d memory_limit=-1 ./occ files_external:notify 5 -v
Self-test successful
added /210422_132820.mp3
An unhandled exception has been thrown:
Error: Call to undefined method OC\DB\ConnectionAdapter::isConnected() in var/www/html/apps/files_external/lib/Command/Notify.php:302
Stack trace:
#0 /var/www/html/apps/files_external/lib/Command/Notify.php(220): OCA\Files_External\Command\Notify->reconnectToDatabase(Object(OC\DB\ConnectionAdapter), Object(Symfony\Component\Console\Output\ConsoleOutput))
#1 /var/www/html/apps/files_external/lib/Command/Notify.php(200): OCA\Files_External\Command\Notify->markParentAsOutdated(5, ‘/210422_132820_…’, Object(Symfony\Component\Console\Output\ConsoleOutput))
#2 /var/www/html/apps/files_external/lib/Lib/Notify/SMBNotifyHandler.php(71): OCA\Files_External\Command\Notify->OCA\Files_External\Command{closure}(Object(OC\Files\Notify\Change))
#3 /var/www/html/apps/files_external/3rdparty/icewind/smb/src/Wrapped/NotifyHandler.php(75): OCA\Files_External\Lib\Notify\SMBNotifyHandler->OCA\Files_External\Lib\Notify{closure}(Object(Icewind\SMB\Change))
#4 /var/www/html/apps/files_external/3rdparty/icewind/smb/src/Wrapped/Connection.php(79): Icewind\SMB\Wrapped\NotifyHandler->Icewind\SMB\Wrapped{closure}(‘0001 210422_132…’)
#5 /var/www/html/apps/files_external/3rdparty/icewind/smb/src/Wrapped/NotifyHandler.php(77): Icewind\SMB\Wrapped\Connection->read(Object(Closure))
#6 /var/www/html/apps/files_external/lib/Lib/Notify/SMBNotifyHandler.php(75): Icewind\SMB\Wrapped\NotifyHandler->listen(Object(Closure))
#7 /var/www/html/apps/files_external/lib/Command/Notify.php(201): OCA\Files_External\Lib\Notify\SMBNotifyHandler->listen(Object(Closure))
#8 /var/www/html/3rdparty/symfony/console/Command/Command.php(255): OCA\Files_External\Command\Notify->execute(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#9 /var/www/html/core/Command/Base.php(169): Symfony\Component\Console\Command\Command->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#10 /var/www/html/3rdparty/symfony/console/Application.php(1009): OC\Core\Command\Base->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#11 /var/www/html/3rdparty/symfony/console/Application.php(273): Symfony\Component\Console\Application->doRunCommand(Object(OCA\Files_External\Command\Notify), Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#12 /var/www/html/3rdparty/symfony/console/Application.php(149): Symfony\Component\Console\Application->doRun(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#13 /var/www/html/lib/private/Console/Application.php(215): Symfony\Component\Console\Application->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#14 /var/www/html/console.php(100): OC\Console\Application->run()
#15 /var/www/html/occ(11): require_once(’/var/www/html/c…’)