I have a workflow running to add a line before record submit based on criteria in the Sales Order Header. To eliminate user time having to add an item. Any clue on why it is not running fast enough before save, which is causing of the issue of not being able to save.

This is not something a workflow does well. In fact I'm shocked you have something working because I didn't even think that was possible. You are probably better off scripting it.

Do you mean when the user saves? When the user saves, first the "Before Record Submit" actions would trigger, then after that the record is saved to the server on NetSuite's side (After Record Submit). These are server triggers, so they happen after the user submits the record (Before/After User Submit). If the Workflow is running on Before Record Submit, that is a server trigger that happens after the user already hit save in the browser (User submit).