What goes wrong with correspondent rails
The specific problem is a breakdown in the payment chain. Your fintech or local bank does not have a direct relationship with the beneficiary's bank, especially if it's in another country. To send your EUR 100,000, they rely on intermediary or correspondent banks. This might involve a large EU bank to process the euro leg of the transaction, which then sends it to another correspondent that holds an account for the final destination bank.
Failure happens when one of these intermediaries gets spooked. Perhaps your company's industry is on their internal, unpublished blacklist. Maybe the jurisdiction of your counterparty is flagged as high-risk. The correspondent bank's compliance team, with no direct relationship to you, has a low threshold for suspicion. They will not ask you for more information; they will simply reject the transaction. The payment then has to travel back through the same chain, often losing fees at each step. In worse cases, they may freeze the funds pending investigation or file a suspicious activity report that can lead your primary bank to off-board you as a client to de-risk their own correspondent relationships.