Matomo Cron Archive Server Errors

Hi,

the archiving process of Matomo stopped working in our setup.
Is see hundreds of such error messages in our log files:

From WP->Matomo->Diagnose:
…
‘Got invalid response from API request: ?module=API&method=CoreAdminHome.archiveReports&idSite=1&period=year&date=2021-01-01&format=json&segment=referrerName%3D%3Dnl_20210912_Reminder&trigger=archivephp. The response was empty. This usually means a server error. A solution to this error is generally to increase the value of \’memory_limit\’ in your php.ini file. For more information and the error message please check in your PHP CLI error log file. As this core:archive command triggers PHP processes over the CLI, you can find where PHP CLI logs are stored by running this command: php -i | grep error_log’ ‘Error unserializing the following response from ?module=API&method=CoreAdminHome.archiveReports&idSite=1&period=year&date=2021-01-01&format=json&segment=referrerName%3D%3Dnl_20210912_Reminder&trigger=archivephp: \’\” ‘548 total errors during this script execution, please investigate and try and fix these errors.’ => ScheduledTasks.php:343; class-wp-hook.php:290; class-wp-hook.php:316; plugin.php:551; wp-cron.php:138;
…

From our PHP error logs:
[24-Sep-2021 04:56:40 UTC] PHP Fatal error: Uncaught Exception: 548 total errors during this script execution, please investigate and try and fix these errors. in [DOCUMENT_ROOT]/wp-content/plugins/matomo/app/core/CronArchive.php:599
Stack trace:
#0 [DOCUMENT_ROOT]/wp-content/plugins/matomo/app/core/CronArchive.php(592): Piwik\CronArchive->logFatalError(‘548 total error…’)
#1 [DOCUMENT_ROOT]/wp-content/plugins/matomo/app/core/CronArchive.php(265): Piwik\CronArchive->end()
#2 [DOCUMENT_ROOT]/wp-content/plugins/matomo/app/core/Access.php(673): Piwik\CronArchive->Piwik\{closure}()
#3 [DOCUMENT_ROOT]/wp-content/plugins/matomo/app/core/CronArchive.php(269): Piwik\Access::doAsSuperUser(Object(Closure))
#4 [DOCUMENT_ROOT]/wp-content/plugins/matomo/classes/WpMatomo/ScheduledTasks.php(330): Piwik\CronArchive->main()
#5 [DOCUMENT_ROOT]/wp-includes/class-wp-hook.php(290): WpMatomo\ScheduledTasks->archive()
#6 [DOCUMENT_ROOT]/wp-includes/class-wp-hook.php(316): WP_Hook->apply in [DOCUMENT_ROOT]/wp-content/plugins/matomo/app/core/CronArchive.php on line 599

Memory Limit is already at 512MB and no SegFaults or what so ever in our log files.

Any advice would be very appreciated.

Best
Max