@disag it sounds like you may need to log a support incident for this in order to have someone investigate this in details.

Did you already check the logs?

When you see the error "Error calculating time elapsed" from the  wizard do you notice a recurring  user id linked to the error?

Before the error, do you see any big jump on "Number of Threads" and " Request count"?  

Can you replicate this consistently?

If you need a more in-depth investigation then our support team will need you to provide a document with detailed steps and screenshots in reproducing the issue.   Make sure to include the screenshots of configuration while using the integration wizard.

Please include the full PegaRULEs and Alerts logs covering the timeframe of the reproduction when you log the support ticket.

If you log the support ticket, please can you provide us the INC number here?