Not installing default route in routing table

Hello all:

I am receiving default routes from IBGP on both WAN1 and WAN2 but it is not getting installed in the routing table. 

When I check received route from both IBGP peers on firewall, I see receiving default but nothing goes to routing table. 

If I configure static default towards both peers, then in routing table I see static configured and also see B route in RIB table too.

Any one had this kind of issue or some one have any idea what is causing this issue.

Thanks in advance