Issue refreshing timestamp edit docs

Good morning everyone, on a new installation of Nextcloud version 27.1.6 with onlyoffice 8.2.4 and Community Document Server 0.1.15 in order to update the timestamp of file modifications and to update the file to the latest editing executions (up to version 26 ) a cron job that executed the command e.g. sleep 20; /usr/local/bin/php -q /home/vdfwlisq/public_html/www/stage/stored/occ documentserver:flush but I get the following errors:

TypeError: Return value of "OCA\DocumentServer\Command\FlushChanges::execute()" must be of the type int, "null" returned. in /home/vdfwlisq/public_html/www/stage/stored/3rdparty/symfony/console/Command/Command.php:301
Stack traces:
#0 /home/vdfwlisq/public_html/www/stage/stored/core/Command/Base.php(177): Symfony\Component\Console\Command\Command->run()
#1 /home/vdfwlisq/public_html/www/stage/stored/3rdparty/symfony/console/Application.php(1040): OC\Core\Command\Base->run()
#2 /home/vdfwlisq/public_html/www/stage/stored/3rdparty/symfony/console/Application.php(301): Symfony\Component\Console\Application->doRunCommand()
#3 /home/vdfwlisq/public_html/www/stage/stored/3rdparty/symfony/console/Application.php(171): Symfony\Component\Console\Application->doRun()
#4 /home/vdfwlisq/public_html/www/stage/stored/lib/private/Console/Application.php(211): Symfony\Component\Console\Application->run()
#5 /home/vdfwlisq/public_html/www/stage/stored/console.php(100): OC\Console\Application->run()
#6 /home/vdfwlisq/public_html/www/stage/stored/occ(11): require_once('/home/vdfwlisq/...')
#7 {main}

I have the impression that despite these messages the command works (in fact the modified files are updated), but I don’t understand these warnings.
One thing I notice is that if I launch the “documentserver:flush” command from the console with OCC web everything works correctly without receiving errors. Could anyone help me on this.
A thousand thanks
Ale