CWTKA0146E The specified template-based task instance ''`0`'' cannot be migrated to an ad hoc task.

Explanation
Template-based task instances must stay template-based.
User response
Try one of the following actions: In your runtime client, jump to an activity in the process that is before the specified task instance, and retry the migration. Add the task template for the task instance, and try to migrate the process instance to the new template.