Thank you for the response, Fausto.
The 259 error just occurred once, and as I said, may not be related to the communication error.
The communication error has been an issue from the start. The USB-2416 is installed in a system that we shipped to Algeria and it is there now. At first, with all of our testing and starting and stopping of the operating system, we ignored the problem and thought it would go away once we were in a stable operating environment. But it has not gone away. It seems to occur at random times, maybe once per day or less. And it seems to occur when the system is idle and not collecting data. When it is actively collecting data it seems to be ok.
I do not have another unit to swap out or test. If it is defective, I will need to ship a new unit to Algeria and then wait for the old one to return. We cannot ship from Algeria first, as this would cause the system to go down.
Although the unit was purchased 2 years ago, it has only been operating for a few months because of Covid causing Algeria to close its borders for a prolonged time. We are still in a system-commissioning mode, and so warranty replacement would be appreciated even though we are beyond the original 1-year warranty.
It is S/N 1EF9CA6, P/N 199082C-02L.
Thank you for your help and suggestions.