The failed transactions that was common around that time were online ones made on devices and which is still a problem today. It was common during the naira scarcity. Sometimes, the payment might be successful, but no notification. It depends on the bank that you are using. I do not have the problem with the bank that I use.
And with all these wallets present now they are in serious competition with our commercial banks and the majority of them don't even have customers like before because if you look at all these wallets give better offers than our commercial banks. they give free transfers and have limited charges compared to our commercial banks. and truely that our banks have improved because you will always have one or two issues with the bank but this day's people hardly go to the bank their network is better. and during festive seasons network used to be worse because of transactions but thank God it was fair enough last year.
during the naira scarcity, people were even switching from banks to using opay and others because of their lightning network as you send the money going with delay compared to our banks but good for them that they have improved and even introduced other means of doing transactions than just using mobile apps and the ussd code.