Hi Blake,
Sorry for the late reply. Generally, TxnLineID sync errors for sales orders are due to either the line already being invoiced, or the item not syncing over to QB yet.
Given that you were able to re-add the item and have the conflict go away, leads me to believe that the item hasn't synced or is in conflict for some reason.
I see that we have a case created for you. I'll reach out via the case for more information on these conflicts.
- Adam