Phil,

This is erroneous behavior indeed.  Have you checked to ensure that no accounts potential have changed on the servers?  Odd that everything is still working also and yet you get the errors.  You mentioned SharePoint errors, but have you looked at the ULS logs to see if anything is showing there? 

What version of Nintex are you on? 

Any chance you are getting this error after a Pause action? It was the case in my situation and I fixed it by disabling Workflow Timer Service on my APP server where Web App Service was also disabled. Both should be enabled on WFE servers.

Hi, thanks for the response.    Our installed
version is 2010,  (2.0.0.6)   with an enterprise license.

Regarding the ULS  logs- I am not finding anything of
substance at or around the times of the workflow failures.   I’ll try
to look at a larger sample for more clues.  

Hmm thanks for the suggestion.  Both services are running
on the app and on the web server.  I can try disabling them on the app
server as you have suggested.   There are several workflows that have
pauses and wait for update steps that are failing (but succeeding).  But
it is strange this service configuration has been working up until this point.

Thank you

Just to make sure we are on the same page. You only need to disable the Workflow Timer Service if the Web App Service is already

disabled. Here are the details and some other options for you:

https://support.microsoft.com/en-us/kb/2674684

Hi , 

Were you able to find the resolution to your problem? We are experiencing similar issues with workflows randomly erroring out. They seem to work sometimes and other times we get these errors without any modifications to the workflow or list. 

Thanks, 

Ivan

We have the same issue here.  Some workflows randomly show the "An error has occurred" message.  The workflow completes all steps.  There are no relevant error messages in ULS.  The actual cause of the error seems to be that it reaches an idle timeout.  We tried adding Pause to the start and end of the workflow but it does not work.  More of a nuisance than a real problem.

Having the same issue with SP2013 on a new workflow. Occasionally, and seemingly at random, I find items with the status "Failed on Start" and "Failed on Start (retrying)". History log entries, along with analysis of the results indicate that the workflows have run; however, because they are in error, new instances of the workflow can't be started until the error clears.

This is the same list where I'm having another issue Intermittent Errors Updating List Item and Setting Permissions and this workflow was created in an attempt to resolve the issues experienced with that workflow. So maybe it's the list? This is a very large list (approaching 10K items) that sees a great deal of activity, has multiple content types, a lot of fields including several calculated fields.

So rediscovered this post while two years later troubleshooting the same problem. Workflow instances randomly run to completion but show "incomplete" and eventually just throw an error. 

I think putting an "End Workflow" action here has reduced the frequency of the problem. Will try.