Disgustingly slow transfer in one direction

Hi guys,

Thanks for the replies.  Glad to say I've fixed the issue!  I'm putting some detail in here in the hope it helps someone..

I have 2 x gigabit network adapters in my Win10 PC.  One is Realtek (what I've been using until now) and one is Intel (previously unused).

I swapped my network cable over to the Intel port and set up the adapter with the same config.  After some initial pain (the result of a static ARP entry in the router pointing the IP to the old Realtek adapter) I found the problem vanished.  Immediately.

File transfers from both my ReadyNAS devices to my Win10 computer absolutely flying at around 100MB/sec.  Something very odd with the combination of this Realtek adapter, the ReadyNAS devices (remember it didnt affect my FreeNAS box) and the direction of traffic (ReadyNAS to Win10 only affected).  

StephenB - To answer your questions, no IPV6 and no NIC bonding. 

RolandWausE - Thanks for the tip, I'll check this out anyway.

So yeah.  One last thing of interest, I noticed the file transfer speed during the height ofthe issue was 355kb/sec.  A quick google for "slow transfer 355kb/sec" returned HEAPS of results for people finding transfer speeds capped at this rate. 

Maybe a simple driver update on the Realtek adapter will sort it out, but I'm too scared to touch anything at the moment.  I'll update if I ever work it out properly.