IPsec tunnel failing frequently..

Hello, Having issues keeping a IPsec Site-to-Site tunnel up..

I am having FG60D device successfully connect to azure using FortiGate Cookbook - IPsec VPN to Microsoft Azure (5.2)  

but tunnel got disconnect frequently in few hours and Had to reboot 60D always to get the tunnel bring up

firmware version : V5.2.6, build711

phase 1 proposal :

encryption AES 128 authentication SHA256

encryption AES 256 authentication SHA256

encryption AES 128 authentication SHA1

encryption AES 256 authentication SHA1

Diffie-Hellman group       : 2

key lifetime                    : 56600 seconds

phase 2 proposal :

encryption AES 128 authentication SMA1

encryption AES 256 authentication SHA1

encryption AES 128 authentication SHA256

encryption AES 256 authentication SHA256

Replay detection [enabled]

PFS                    [enabled]

Diffie-Hellman group    : 2

Local Port            [enabled]

Remote port        [enabled]

Protocol              [enabled]

Autokey keep Alive  [enabled]

Auto-negotiate        [enabled]

key lifetime             : 7200 seconds

It seems known problem in 60D

Any help is highly appreciated,

Thanks!

Nihal