We have been dealing with seemingly random transaction failures recently. We are using paypal payflow pro and we have had issues running credit cards through the admin panel as well as the checkout page. The majority of the transactions are going through, but these random outliers keep coming up. The magento error messages are not particularly helpful and we are having a very hard time troubleshooting what may be causing the payments to not come through.
One piece of info we got was that the customer called their bank and they mentioned that a transaction was passed but it came out to 0 dollars so they canceled it.
It FEELS like the banks are declining the orders but this seems too common to be true. We did recently launch this site, previously a magento 1 site, now a 2.3.1 site.
Edit: Looking into our paypal merchant account, we see ALL o our transactions coming in as 0 dollars