Traverse packets dropping frequently

Hi,

On brand new XGS-136 I have problem, which cannot solve for few days. So I would appreciate any hints.

Packets are dropping randomly every minute or so, sometimes even more frequently, in the following direction:

• From LAN side --> to Sophos LAN adapter IP (192.168.1.2 below)
• From LAN side --> via Sophos LAN --> towards and IPSec Site2Site tunnel (192.168.80.1 example below)
• From LAN side --> via Sophos --> to Google DNS (8.8.8.8 in example below)

But packets are NOT dropping:

• From Sophos CONSOLE --> to any IPSec VPN tunnel (192.168.80.1 example on far left)
• From ANY LAN device --> to ANY other LAN device, except Sophos (I have no example, but I was testing for a day and no lost packets)

IPS is DISABLED.
DDos is DISABLED
Any WEB filtering proxy is disabled.
Firmware is latest.

I have no idea what's going on. Anyone?