Tax Not Calculating After 12.1.3+ Upgrade

Hello, All.

After recently installing RPC4, we have noticed tax is not calculating for some invoices.  One invoice in particular - prior to patching - was paid, but showed a status of Needs Revalidation.  Now the tax line on that invoice has reversed, the invoice is out of balance, and it is on hold.  Has anyone experienced anything similar?  One thing I did notice is generate_dists = Y in ap_invoice_lines_all table; could that be part of the problem or do you think it is something else?

The invoice now Needs Revalidation, is partially Accounted, and some accounting lines are unprocessed.  Any help you can give is greatly appreciated.