I just added a new node to NPM, and it overwrote an existing node. It's not a case of a duplicate IP (though I haven't gone back very far to confirm that the older device never used that IP). Fortunately, the device in question doesn't have customer connections, so no harm done in regards to billing this time. The only time I've ever seen this happen before is if I try to add a node by IP that is already being monitored. Is this something that's been known to happen, or did I just get "lucky"?