are you sure that MTU is 1600 across site??
Looks to be mtu issue on physical network.
Can you confirm if we have 1600 mtu confiured between source and dest. hosts.
ping ++netstack=vxlan –d –s 1572 –I vmkX IP_address_of_destinataion_host_vmk
From this key point 'Ping/telnet is absolutely working fine hence no routing issues.' VM A can ping VM B?. If so we've to look into firewall which may be blocking http/https traffic.
Have you tried to access the VAMIs from the same subnet?
I've had issues where VAMI access did not work when coming from another subnet (routed).