Unfortunately, there’s no supported way to change the implementation type of already active tasks from job worker to Camunda User Task in running instances. I found the following relevant resources:
- Process instance migration limitations - Migration cannot change task implementation types
- Migrate to Camunda user tasks guide - Shows how to migrate for new instances only
- Forum discussion on similar migration challenges - Community experience with active process migration issues
Does this help? If not, can anyone from the community jump in? 
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