Serialization error while archiving

My archive cronjob always breaks for a specific tracked URL. In DataTable.php I found that function unserializeRows (line 1465) always evaluates $rows to false, i.e throws “The unserialization has failed!” even if there is a regular looking array.

Testing archivephp with other tracked URLs returns regular json:
{“idarchives”:[296176],“nb_visits”:1166}

I used the following console command for testing archivephp:
/usr/bin/php /var/www/piwik/console climulti:request --matomo-domain=“https://xxx” --superuser “module=API&method=CoreAdminHome.archiveReports&idSite=58&period=year&date=2024-01-01&format=json&trigger=archivephp”

I already tried increasing memory and max_execution. I am working with Matomo 5.1.2 and php 8.3; charset for all table is utf8m4 and collation utf8mb4_general_ci.

Has anyone an idea where to check more for the error?

Thank you