Ok I just checked all the code paths where the private key is set and its possible to turn a read-only account into a normal account by entering the private key, but it doesn’t check if the private key belongs to that read-only account, oops  😬

So what probably happened is you had a read-only with your main account and then at some point turned it to a normal account but with a different nsec.

If you have a Mac with iCloud keychain sync you could manually fix this in Keychain Access, on the phone its not possible I think, I’ll need to add some tooling in Nostur to recover from this.