Possibly unrelated but maybe worth checking (as without detailed packet analysis I would not make any assumptions)
- Is RX and TX Flow Control disabled as per best practice?
p7-8 of:
Check if is enabled using:
# ethtool -a vmnic<#OfNic(s)InUseForVsanTrafficHere>
Set to off:
# ethtool --pause VMNic_Name tx off rx off
More info:
https://kb.vmware.com/kb/1013413
(checked and set on every host in the vSAN cluster of course)
Bob