If anybody had said there is ever a problem with fiat currency, then I stand to disproof that as fiat has never got any problem, but rather has it's advantage and disadvantages when compared to Bitcoin, which happens to be the decentralized digital currency.

Yes, that is what we were told, but I have personally witnessed a scenario where a transaction which was executed was reverse 4 days later due to low fees to get the transaction into any available block on the Blockchain during the period when the mempool was congested. And the luck I had was that both Bitcoin wallets were mine, as I was trying to send the coin from my  custodian wallet to an exchange wallet.