motti → created an issue.
The error on my custom batch disappeared when adding a redirect on finish. But the message on the configurations-import still persists.
The error still occurs on Version 2.1.0-beta5. We experience it with active PWA Module if we use batch_set() in a custom module. On some other occasions as well. But i'm currently not sure if it was a manual cron-run or cache rebuild.
I got the same problem. My site actual is a new site set up at core version 10.1.x. At that time the problem wasn't there. It first accrued after updating to 10.2.x. The problem might be related somehow to https://www.drupal.org/project/drupal/issues/3411419 🐛 Regression from #2521800: using machine name element for ListStringItem breaks with existing data Fixed ?