Strange network issue with one VM - Help Needed..

I have a strange issue with a Windows 2012 R2 VM.. Apps team said they were having an issue transferring a file. They did a running ping from the server doing the transfer to the server receiving the file.. When they specified a byte size of 5000 it would randomly drop pings but the latency was fine.. This is all over the WAN..

To troubleshoot I have done the following:

• When I do a running ping with a packet size of 5000 on another VM on the same host I get no drops from two different WAN core switches.
• Moved VM to another host (even though host not suspected to be issue) - issue persisted.
• Rebooted VM
• Removed VMNIC (was VMXNET3) and Added New VMXNET3 - issue persisted.
• I can ping local LAN physical and virtual servers without issue on the problem VM.

I'm out of ideas of things to try.. If the server can ping local LAN nodes with no issue that would point to it being the WAN, no? But then why are other VMs on the same vmware cluster (and same esxi host) not having the issue??

Thanks for any ideas!