NextcloudPi slow on deleting files

Hi, i am running a nextcloudpi instance on my raspberry pi2 with an external usb hdd and i can perfectly live with the perfomance of the installation, only i have issues with deleting files, no matter if i do it via webdav or webinterface, if i try to delete like 20 mp3 files, it takes way longer than to actually upload them, also meanwhile nextcloud is totally unresponsive and even ssh access to the reaspy is slow.
I am not sure if this is a new problem in latest version, or somehow specific to my installation, anyone an idea how to find that out?

just found out that there seems to be an issue with my files somehow, when scanning for externally modified files (i did not do somthing like this thou, just tried to scan if soemething was wrong there) i get this output:

Exception during scan: “files/bbf0d961829ae353355b7350021c2f87” is locked, existing lock on file: exclusive
#0 /var/www/nextcloud/lib/private/Files/Storage/Common.php(709): OC\Lock\MemcacheLockingProvider->acquireLock(‘files/bbf0d9618…’, 2)
#1 /var/www/nextcloud/lib/private/Files/Storage/Wrapper/Wrapper.php(592): OC\Files\Storage\Common->acquireLock(‘scanner::’, 2, Object(OC\Lock\MemcacheLockingProvider))
#2 /var/www/nextcloud/lib/private/Files/Cache/Scanner.php(331): OC\Files\Storage\Wrapper\Wrapper->acquireLock(‘scanner::’, 2, Object(OC\Lock\MemcacheLockingProvider))
#3 /var/www/nextcloud/lib/private/Files/Utils/Scanner.php(240): OC\Files\Cache\Scanner->scan(’’, true, 3)
#4 /var/www/nextcloud/apps/files/lib/Command/Scan.php(161): OC\Files\Utils\Scanner->scan(’/Gerd’)
#5 /var/www/nextcloud/apps/files/lib/Command/Scan.php(234): OCA\Files\Command\Scan->scanFiles(‘Gerd’, ‘/Gerd’, false, Object(Symfony\Component\Console\Output\ConsoleOutput), false)
#6 /var/www/nextcloud/3rdparty/symfony/console/Command/Command.php(264): OCA\Files\Command\Scan->execute(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#7 /var/www/nextcloud/core/Command/Base.php(162): Symfony\Component\Console\Command\Command->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#8 /var/www/nextcloud/3rdparty/symfony/console/Application.php(874): OC\Core\Command\Base->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#9 /var/www/nextcloud/3rdparty/symfony/console/Application.php(228): Symfony\Component\Console\Application->doRunCommand(Object(OCA\Files\Command\Scan), Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#10 /var/www/nextcloud/3rdparty/symfony/console/Application.php(130): Symfony\Component\Console\Application->doRun(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#11 /var/www/nextcloud/lib/private/Console/Application.php(173): Symfony\Component\Console\Application->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#12 /var/www/nextcloud/console.php(90): OC\Console\Application->run()
#13 /var/www/nextcloud/occ(11): require_once(’/var/www/nextcl…’)
#14 {main}