WINS Replication

I have NT WINS Servers in 13 remote sites all configured as push/pull partners with a central office WINS Server. All intervals are configured identically; all push/pull partners are configued with identical intervals. 11 of the site replicate faithfully as scheduled; 2 do not. The only difference I can see when looking at WINS on these ornery servers is that when viewing the database, the button labeled DELETE MAPPING is not present. Why is this and is it affecting replication?