Well, just some thoughts to troubleshoot the issue, seeing as you're getting throughput problems.
I design networks and would look at source to destination type controls like flow control for an answer to that.
I have to say I have a NAS setup and use MKV contained movies, and have not run into a full freeze while playing. I'm not sure I've seen any freezes.
May be just luck, but I did tune the network with each new component I've added, since I don't want to get any issues.
Anyways, good luck, it's unfortunate you haven't been able to get the same performance I'm getting.