Hi infopathman,
Is this an IPFS form? My memory is a little vague, but I remember working with an browser form (no Qdabra products involved) where locking was not respected by Sharepoint itself, and users could overwrite each other. I would need to recreate the scenario to confirm.
But anyway, to get to the bottom of this, what does your submit button do? Does it
submit via the DBXLDocumentService > SubmitDocument?