The person who you've quoted is most likly just a scammer.
Because there's no convenient solution to that issue since it will not be created by accident or through errors.
The "solution" is to find the address's private key or the watch-only wallet's master public key's 'seed phrase'/'master private key' to create a non-watching only wallet.

You must have imported an address(es) or master public key to create the wallet or it's from someone else,
there are no other means of creating a watch-only wallet other than those options.