Does it mean that unconnected invoice line exist in the analyze step? Is this freight cost a separate invoice line or one invoice line contains material and freight cost?
Do you use auto coding for deviations and exception types?

Suggested solution could be to use our document validation rule framework to redirect those invoices to proper person.
The invoice will still end up in Post Control but you can specify that for instance invoices that are not in balance should be directed to a specific user or role.
Will this be sufficient?
https://success.mediusflow.com/documentation/administration_guide/administration_pages/document_validation_rule/#content-start

We have found that PO based invoices appearing in Post Control are not always fully balanced. This might be due to that e.g. a freight cost has not been coded/caught by any exception. We would like unbalanced PO based invoices to be haltered and managed in the Analyze step (as in Mediusflow 10) so that in our case the Procurement department are forced to book/accept e.g. the freight cost.
Since it is our Finance department in some of our subsidiaries who final book PO based invoices they are not always aware if any un-coded freight cost is OK to pay or not.

Limit the possibility for a orderbased invoice goes directly to post control eventhoug its not fully coded.
When a OB invoice is connected and lines are matching the invoice is send directly to Post control, eventhough the invoice is not finished.