Strange Problem With Copying Files on IPSec

[acp]

We have a IPSec Site to Site VPN from our London office to our India office.

We have recently noticed a strange issue where copying files from a Windows Server 2012 and 2008R2 machine in the London office to another Windows 10 machine in the India office hangs and doesn't do anything.

But when copying from a Linux machine in London to a Windows 10 machine in India it works fine at around 4-8Mbps.
And copying from a Windows 7 machine in London to a Windows 10 machine in India it works fine at around 8Mbps.

We tested it multiple times and Windows - Windows file transfer hangs while Linux - Windows or Linux to Linux works fine.

Edit: After more testing we have noticed we have the hang issue on machines that are on the windows domain but it works fine with machines that aren't on the domain.