Interrupting connections with SG4400 R77.30

[kazgov]

Hello! We have a Checkpoint SG4400 with R77.30. There is a problem with very often interrupting connection to local network (through the Site-to-Site VPN tunnel with Palo Alto 3020). It happens in a different moments (2-4 times a day). The tunnel is active during these interruptions. The public IP is available at these moments. There is no dropped or rejected packets in Smartview Tracker at this time. What would it be and how can I fix this issue?