Every once in awhile, I notice when running and/or testing automation(s), they run as expected, but then all of a sudden something happens within the existing applications, platforms or systems to cause an unexpected Window or Dialog Box to be presented.
I do know that UiPath does have Event Type Triggers, so my suggestion would be to have the ability for an automation process to be able to define a trigger that could be executed when one of the unexpected Windows or Dialogs is encounter, but the trick is for the main automation flow to be paused at it;s current execution point and then be resumed after the Event Trigger has completed dealing with the Window or Dialog.