We have implemented the following logic:
When you have sent the invoice, the invoice is frozen;
If you change the master data afterwards, old invoices will NOT take on this master data change;
If you decide to resend an invoice, the incorrect invoice will be resent.
You have to release the old invoice first, then the invoice automatically takes on the updated master data.
Only then can you resend the invoice (which is saved automatically) or save and send it.