We have a production server with paypal payment that is working properly in regular basis. But from time to time, we have missing orders for paid carts.
After some debugging, we have found a direct relation between a connection error with Paypal and those missing orders. The most common error is: PayPal NVP CURL connection error #28.
We figure out it can be in moment in which we have a high load, or maybe because there is a high load on Paypal servers.
The real problem here is not a puntual "can't connect" error, but the missing order. I think the flow should be to allow a communication retry after some kind of errors... o add a new status "Can't verify payment" to mark it as there was some problem and the payment can't be verified.
Anyone else has found with this situation? I found no info in the forum or stackexchange about this case or similar.