NSeries OSPF Default Routes Resetting

Topology

Issue: Default Route Age of NSeries resets upon OSPF adjacency change, causes partial outage as well

Overview:
S4200 ASBRs advertising default routes to NSeries, NSeries route table below have 2 default ECMP routes, when one of OSPF adjacency change the route age also resets for the other default route advertisement, see image below same route age uptime. 

NSeries Route Table when both adjacency are up