Sharepoint 2013 (Workflow engine 2010), Nintex Workflow and Forms 2013,
After responding to a flexitask of a site workflow the comment field of task item will be updated but the workflow will stay incomplete and pending and the task is locked thereafter (Error This task is currently locked by a running workflow and cannot be edited.).
I can unlock the task by PowerShell script as described in Task Lock - Task is locked by a running workflow and cannot be edited , but then same behaviour occurs.
Workflow instances have been running for months without problems. No modifications were made.
Any ideas how to complete the task so the workflow will continue?