User sync errors desktop app <-> nextcloud server

I have issues for two users whereby the desktop app is throwing sync issues. These users can access nextcloud from the browser without any problems.

I have made a force scan using the following:

cd /var/www/nextcloud
sudo -u www-data php console.php files:scan username

And I get the error as follows:

Starting scan for user 1 out of 1 (username)
Exception while scanning: "files/bffeac5f086778022d7ef8d8912964c4" is locked
#0 /var/www/nextcloud/lib/private/Files/Storage/Common.php(651): OC\Lock\DBLockingProvider->acquireLock('files/bffeac5f0...', 2)
#1 /var/www/nextcloud/lib/private/Files/Storage/Wrapper/Wrapper.php(584): OC\Files\Storage\Common->acquireLock('Council Purchas...', 2, Object(OC\Lock\DBLockingProvider))
#2 /var/www/nextcloud/lib/private/Files/Storage/Wrapper/Wrapper.php(584): OC\Files\Storage\Wrapper\Wrapper->acquireLock('Council Purchas...', 2, Object(OC\Lock\DBLockingProvider))
#3 /var/www/nextcloud/apps/files_sharing/lib/sharedstorage.php(365): OC\Files\Storage\Wrapper\Wrapper->acquireLock('Council Purchas...', 2, Object(OC\Lock\DBLockingProvider))
#4 /var/www/nextcloud/lib/private/Files/Storage/Wrapper/Wrapper.php(584): OC\Files\Storage\Shared->acquireLock('scanner::', 2, Object(OC\Lock\DBLockingProvider))
#5 /var/www/nextcloud/lib/private/Files/Cache/Scanner.php(306): OC\Files\Storage\Wrapper\Wrapper->acquireLock('scanner::', 2, Object(OC\Lock\DBLockingProvider))
#6 /var/www/nextcloud/lib/private/Files/Utils/Scanner.php(196): OC\Files\Cache\Scanner->scan('', true, 3)
#7 /var/www/nextcloud/apps/files/lib/Command/Scan.php(159): OC\Files\Utils\Scanner->scan('/diacc004')
#8 /var/www/nextcloud/apps/files/lib/Command/Scan.php(227): OCA\Files\Command\Scan->scanFiles('diacc004', '/diacc004', false, Object(Symfony\Component\Console\Output\ConsoleOutput), false)
#9 /var/www/nextcloud/3rdparty/symfony/console/Command/Command.php(259): OCA\Files\Command\Scan->execute(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#10 /var/www/nextcloud/core/Command/Base.php(159): Symfony\Component\Console\Command\Command->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#11 /var/www/nextcloud/3rdparty/symfony/console/Application.php(844): OC\Core\Command\Base->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#12 /var/www/nextcloud/3rdparty/symfony/console/Application.php(192): Symfony\Component\Console\Application->doRunCommand(Object(OCA\Files\Command\Scan), Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#13 /var/www/nextcloud/3rdparty/symfony/console/Application.php(123): Symfony\Component\Console\Application->doRun(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#14 /var/www/nextcloud/lib/private/Console/Application.php(146): Symfony\Component\Console\Application->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#15 /var/www/nextcloud/console.php(90): OC\Console\Application->run()
#16 {main}

+---------+-------+--------------+
| Folders | Files | Elapsed time |
+---------+-------+--------------+
| 31      | 1285  | 00:01:19     |
+---------+-------+--------------+

All other users have no issues.

What is the cause of this error and how can I solve it please?