When running SPF on an NSSA, the router-ids of the current routers in the area are always copied into a temporary list. However, this temporary list is only later freed on the master and not on the standby. This causes a memory leak in OSPF with NSSA.
After sometime the member is rebooted the value of the OSPF memory is not matching at all.
Example:
Active-FW1:1> show routed memory
show instance 1 routed memory
OSPF: 351 Kbytes
MFC: 236 bytes
Core: 390 Kbytes
Standby-FW1:1> show routed memory
show instance 1 routed memory
OSPF: 12298 Kbytes
MFC: 236 bytes
Core: 359 Kbytes