This is because the document the user is looking at has been updated and the one they are looking at is not the updated version. If the user were to refresh after saving (when the business event has changed a field value) then there would be no problem. Instead, if the user continues to work on the document after saving/updating and they are actually working on an old version of that document which is why they get the error upon saving.
What is needed is a way to create a business event that will update the record AND do a refresh of sorts. One of these ways is to click on CANCEL after clicking on SAVE. CANCEL will bring into the document the latest updated values.
Has anyone found a way to refresh/re-cache the document in a users browser after updating it via import scenario or actions? I know I can get around the issue by putting it on a schedule or setting a timer to update after the user has terminated working on the document but this is something that really handicaps the import scenario and actions subscribers imo.
-David