Network stuff can be a tricky thing, routers in particular. There's tons more going on there than most people realize. It's not like electricity where it works or not. There's tons of settings and options that can impact performance, and the "automatic" modes aren't all that effective.
In the cases where people are having network related issues, I'd start by swapping out data ports. Occasionally, a single port on a switch or router can go bad.
Next, swap out ethernet cables. While they don't usually go bad, it can happen. The results could be simply no data, or it could be intermittent data loss, which is much more difficult to diagnose.
If those don't fix the problem, you might try updating router firmware, factory resetting the router, or even changing your router. As an example, not every router is compatible with Apple's Time Capsule or Microsoft's X-Box.
At the end of the day, if you send your BDP into Bryston and they can't duplicate the problem, then the problem isn't likely with the BDP.