I think this happened to me. I signed up to one of the clients, and it somehow changed my LN address to something I was using previously.
In a world in which many Nostr: clients are waiting to be tried and each of them may modify your metadata events in an unpredictable way, having a safe base with data stored locally like https://github.com/mikedilger/gossip gives me a lot of peace of mind.
I think this happened to me. I signed up to one of the clients, and it somehow changed my LN address to something I was using previously.