I'm not sure if this is related but a similar error was reported in Defect 479882 : NetSuite for Outlook > Login Credentials Window Keep Popping Up. You can submit the error logs from your plugin and Support will investigate this further. Definitely related, logs submitted, hopefully it helps! As outlined by my colleague…

I assume this is a large workflow, I am also assuming that It's sitting at a particular point in your flow waiting to go to the next state or a particular piece of logic to be met. You need to make sure that your states have proper termination that account for the user action on the custom form field. What I'd explore is…