add update activity requests errors

I need some advice about a problem we are having.  We have a small essentials app designed to let 10 or less users add or update attributes on  some point data.  the workflow is successful when only one person is running it.  But in our training session all 10 people signed in and started using the application at the same time,  then they all started gettng errors in the update process.  The app uses a workflow that takes  use input from a form activity and then  uses the add new record activity.  Are there settings I can change to increase the rest sites ability to handle many update requests at the same time? or can I change the way the programs executes the adddata edit  activity in workflow to run async instead of sync?  I am open to suggestions and they would be greatly appreciated.

Jeff