ADVPN - Hub and spoke - All tunnels hangs after HA switch

[pacionet]

Hi,

we set up an ADVPN Hub and Spoke VPN where:

• HUB are 2 Fortigate 2600F in Active-Passive HA configuration
• Spokes are Fortigate 60F

Firmware is 7.4.9 version

The VPN works fine, anyway we have problems when some bad events occurs. For example if power goes off or the Hub lost some connectivity and HA switch the primary node, all IPSEC tunnels hangs (they are up but not working)

The only way to resume them is to restart every tunnel spoke side (waiting at least 10 seconds between down and up)

Does exist a way to avoid this situation? Why the HA switch causes the hanging?

Thanks