Do you have more machines on those hosts which uses the same interfaces? are you copying over files or similar?
Yes, I have several other VM's similarly configured, and they can transfer files without issues.
Not sure what about these 2 VM's that is causing the problem.
Aditionally, when I transfer the file from VM1 -> physical host and then from physical host -> VM2, those transfers run at the expected/normal speeds for Gigabit ethernet.
It's only when I go directly between the 2 VMs that the issue presents itself.
Try to create new vSwitch without physical NIC, put both VMs into and try to check network speed between them.
We ended up resolving this issue by changing some settings on the vswitch.
Can you share the setting which helped to resolve your issue