Every 30seconds, a router receives from one of its neighbors RIP updates for a specific route. Suddenly that route gets down and then the router received immediately triggered update from that neighbor for that route, now with metric=16. The route is immediately removed from its routing table, though for the next 60 seconds it keeps advertising this route to all its neighbors, with metric=16. After that it stops advertising the route.
Any idea where those 60seconds are coming from???