I'm testing this with a simple workflow:
- Log message "Workflow has started"
- Assign a To-do item
- Log message "Task is completed"
Here's what we did to make it stop working:
We went and changed site column "Task Status". We deleted all the choices and entered different ones.
At that moment first message was logged, the user could open the task and click complete task button. The workflow did not continue (the second message did not log). Looking into Workflow Tasks list, we saw the fields Status, % Completed and Outcome are blank.
What we tried after realizing this was somewhat completely bad idea:
We then changed choices on site column "Task Status" back to original values and made sure we update all list columns based on this.
Now the field Status in Workflow Tasks list gets updated to "Completed" after we click "Complete Task" on task form, but % Completed and Outcome are still blank.
What have we checked
We compared content type and site column XMLs to unaffected site's XMLs and it seems the same (difference is that affected site column has a bit more attributes like ReadOnly, Version..., but they are set to default values)
Looking into SharePoint logs and Event log showed no errors or anything out of the ordinary.
I found a similar problem on internet when Assigned To field is changed to allow multiple values (the workflow cannot update it and therefor hangs), but it seems my fields are the same as out-of-the-box.
I'm looking for some ideas of how to resolve this. Is there another log where I can look to? Have I missed something when I updated the field back?