Users are not able to approve the invoices due to error message An error occured

Summary:

We have recently modified one PO based Invoice rule by adding discard condition in BPM workflow rules, and the code is working fine for the freshly created Invoices, however, this migration broke all the inflight Invoice Approvals.

For all the in-flight invoice approvals - respective invoice approvers were unable to approve them.

The only option to resolve this is to withdraw and resubmit Invoices to make sure the approvals are re-triggered again, and approvers can act on them.

I have gone through the document Doc ID 2799256.1 and it will not be helpful in our case. The description was easy to understand. can you please let us know how I can setup additional lines without affecting the already submitted invoices? This is a simple change, but we anticipate major changes in future that will add more conditions. How can we handle those situations, or what is the best practice to add them without affecting the already submitted invoices?