Fortigate 500E appears to be not load balancing throughput properly

Fortigate 500E appears to be not load balancing throughput properly V6.2.3

I have a 2-Nod cluster running since the launch of the 500E hardware

Over time, sometimes, we have some sync problems

In the last months we were struggling with a problem related to a non-synch cluster and, at the end, it was an old and expired certificate. After the removal of the vpn.certificate.ca, the problem was partially solved

But..

After a while we noticed that our A-A cluster is load balancing the session, now, 18K sessions per node, but most of the time, Master is processing 50-100 Mbps throughput, but Slave node is processing  between 25-900Kbps

Most of the users are in home, so we´re using VPNSSL and sometimes pptpD, but it shuould laod balance trhoughput even that way, am I right?

get system performance status | grep network Average network usage: 65936 / 68076 kbps in 1 minute, 71031 / 72909 kbps in 10 minutes, 67995 / 69644 kbps in 30 minutes

get system performance status | grep network Average network usage: 2383 / 443 kbps in 1 minute, 2533 / 460 kbps in 10 minutes, 2227 / 436 kbps in 30 minutes

users also complanin about some disconenctyins, TS/RDP session being disconencted with no reason, http session dying and mannually being refreshd to get back, weird behaviour

CPUs are under 5% and Memory below 30% on both nodes (less usage on Slave)

config system ha set mode a-a set sync-packet-balance disable unset session-sync-dev set route-ttl 10 set route-wait 0 set route-hold 10 set multicast-ttl 600 set sync-config enable set encryption disable set authentication disable set hb-interval 2 set hb-lost-threshold 6 set hello-holddown 20 set gratuitous-arps enable set arps 5 set arps-interval 8 set session-pickup enable set session-pickup-connectionless enable set session-pickup-expectation disable set session-pickup-delay disable set link-failed-signal disable set uninterruptible-upgrade enable set ha-mgmt-status disable set ha-eth-type "8890" set hc-eth-type "8891" set l2ep-eth-type "8893" set ha-uptime-diff-margin 300 set vcluster2 disable set override disable set priority 130 set schedule weight-round-robin unset monitor unset pingserver-monitor-interface unset vdom set ssd-failover disable set memory-compatible-mode disable set inter-cluster-session-sync disable set load-balance-all enable end