@davidvd: if you submit a support ticket, we can send you a replacement unit so you can check if it improves the connection. In the end I think the issue is that every user has a different network setup, and the open-source library based on Microchip’s ENC28J60 chip is probably not the most reliable one that fits all different network setups. In the lab we’ve tested and couldn’t find any obvious problem; in the wild it may present issues but we don’t have the resources of testing every possible router / network setup out there. If the replacement unit works, at least we can gain some information about the issue.