It is very common sometimes when we trade on exchange p2p payment delays, these delay can be from the buyer's bank or seller bank's. Many people have lose their money due to this delay of bank network thinking that the problem of the delay is from the network of bank which they will later get their money when the network of their bank becomes good and they go ahead to release the payment because of evidence of payment that the other trader have sent to show as proof.
They were scammed not because of bank transfer delay but because scammers told lies to scam naive traders. That scam trade partner actually does not proceed a bank transfer for the victim. Borrowing a reason like bank delays the transfer to complete a trade between two trade partners is easiest way to lie.
The key rule to avoid scam in peer to peer trading is DON'T release your coins if you have yet received payment from your trade partner. Ignore all things your trade partner chat with you, if you don't receive payment, don't release. You won't be marked as a bad trader because you refuse to release coin in such situation.
Release coin first, before receiving your payment, means you will lose your coin forever. Scammers are very quickly to withdraw coins from successful scam trades and it's not enough time for you to get support from exchanges.