An error occurred while executing WP-CLI command for instance

Hi,

since some days i get the following cron error message:

[2019-06-15 12:53:31.787] ERR [extension/wp-toolkit] An error occurred while executing WP-CLI command for instance: WordPress instance #24
('https://www.xyz.de')

When I execute the command that causes that cron error manually:

/opt/psa/admin/bin/php -dauto_prepend_file=sdk.php '/opt/psa/admin/plib/modules/wp-toolkit/scripts/instances-auto-update.php'

I get the...

An error occurred while executing WP-CLI command for instance