At some site, one NE40 attaches VIP of S8512 and the service interrupts. Check routing entry of matching user on NE40 and the user's route can be learnt. But BGP route is first chosen and the next-hop can change. Check routing entry of the user on another NE40 and OSPF can be learnt.
S8512 attached VIP is connected through electrical interface of O/E converter and S8512 port is self-adaptive. O/E converter is forced full-duplex. It is frequently up/down during negotiation. Change negotiation of S8512 and the service is reachable.
The problem occurs route forwarding of NE40. Check other routing entry on NE40 and the service and forwarding are normal. Remotely land on NE40 attached S8512. Check related interface and routing information of the user, the port is frequently up/down. The link is problematic.