@emha I created a new post with all of the above requested information - would you be able to take a look at it please? https://community.nintex.com/t5/Nintex-for-SharePoint/Workflow-Task-is-Completed-but-Workflow-Outcom...
We've been having this same issue for over a year now, back and forth with the Nintex support team and even they are unsure of the root cause of the issue. Our issue ONLY lies within the lazy approvals though. We cannot process any lazy approvals for a single workflow (our site has 4 primary list workflows made almost identical) and if the user goes to the form for the task it processes perfectly fine. Its only when they try to use lazy approvals to respond to the task that it gets stuck in this "In Progress" mode.
The support guys think it has something to do with permissions, so we shotguned the site and gave everyone full control and it didn't change anything.
When a workflow gets to the "in progress" mode, it NEVER comes back out. We only have one approver as well and their approval comments get processed so we know sharepoint is getting it, but then not completing the task. I was even able to setup a workflow that monitors the workflow task page for any in progress workflows and was able to setup a notification to tell me when one shows up so we can make sure we know when it happens. not that it has helped at all...
Now the real head scratcher here is this: When we first see it, the issue only happens for 24 hours and then everything goes back to normal the next day. In one case we had it go on for 2 days in a row but all the other 50 or so occurrances of this it only goes on for one day. So we know if we hold workflows so they don't go into the approval phase if we wait 24 hours before sending them on they'll work just fine the next day with no changes what so ever to anything on the site. Of course the ones that have already gotten to "in progress" are not able to be kicked over. They have to be stopped and entirely restarted which means the manager has to approve it again. The biggest problem for us is the person who uses the lazy approval process is the last one to approve so we have to go back through the other 3 or 4 approvers before them and it causes a huge headache so we end up just doing a manual approval process for those on paper, which of course is less of a pain for the managers, but more work on the team using the workflow to process these approvals.
All signs point to some kind of permission issue but I don't know what would cause it. its like when the approver goes to make an approval they no longer have access to the workflow task list to update the task so it blows up. But even with full control on the list during the occurance of the issue they still can't update the task list on any tasks using lazy approval and if no permission changes are made and they use the nintex form for the workflow approval task, it works fine even when other lazy approvals are failing for the same user on the same workflow.
Complete head scratcher...
@waltont I feel a bit silly suggesting this since you've been working on it for so long and surely know, but, they aren't modifying the subject line in any way when they reply to the LazyApproval email are they?
I'd have to say the possibility exists, but its highly unlikely due to the nature of the issue. It happens for more tha one user, from completely different departments for a 24 hour period only. If they did it one day, they'd do it the next, or if ONE person was changing it another probably wouldn't. For instance the other day when we had the issue, we had 5 different users have the issue across the entire day. Its been working fine since and we have at least 5 to 10 per day.
Its a viable question though, but the simple answer is I doubt it.