Have you found the fix yet? I have exacally same issue here. S2S VPN between MX100 to FTD. there are 4 vlans on the MX side, We used Ikev1, it has been working fine, until June last year, the tunnel is showing packet drops intermittently, When there are packet drops, i can see vlan4 is not come up as ipsec sa but other vlans are working fine.  ... View more