beire, by any chance, do you have bridge enabled in the unRAID settings ?
I'm preparing a new version with an updated networking library, I hope it solves the issue.
On the other hand, I found the following threads about slow unRAID with bridge mode
https://lime-technology.com/forum/index.php?topic=50224.msg482115#msg482115
https://lime-technology.com/forum/index.php?topic=46516.msg444453#msg444453
saarg, thejamkel and beire, do they ring a bell with your scenario ?
I do not think it's related to the bridge, as I disabled the bridge in my testing and it still didn't work.
I do not experience any of the problems mentioned in the threads you linked.
It would be interesting to know if the others that have problem have a dual CPU setup or supermicro board?