I'm facing a quite strange issue. I have a site collection with many lists and workflows.
Only on my production environnment i have everyday several workflows with the following issue :
Some workflow starts and get completed after few seconds without doing all the tasks expected. The problem is that the workflow history shows that the workflow is completed without executing some actions but in reality some of this actions are partially done. For example the workflow create a flexy task and he should wait until the approver choose "approve" or "reject" but it doesn't and just complete the workflow. So users get notifications, go to the task and then get an error "Nintex.Workflow.NWHumanApprovalException: Cannot find a corresponding human workflow task id for this task".
The site collection contains 109 workflows on 109 lists (one workflow / one form per list). The farm contains 3 front end servers and 2 app servers. I already faced problems when many workflows are executed at the same time, i know that might cause conflicts. But in this specific cas i don't have any workflow errors just workflow completed not doing their jobs and only on production farm on rush hours.
I didn't create those workflows and just start (a few days ago that's why i'm asking) to investigate this problem (that already exists for months now). I plan to make a report off all our customers problems, try to sort only the workflows with this issue and then try to tune them.
Maybe someone faced the same issue and will have an answer / beginning of an explanation...
whenever things go odd the first thing I check if the database version is in synch with the workflow version. Sometimes Nintex updates bring changes to the database model and when certain actions try to call old methods from former versions the database don't understands them and thing go weird.
You can check database version by navigating to Central Administration and open the Nintex Workflow Management section and there the option Database Management
There shouldn't be an "Update now" link visible on that page. Otherwise hit it and update the database schema. Now the workflows should run fine.
Can you try this?