Backup and Restore of master KEY and Certificate are not working on same server but different DBs. I have SQL Server 2012
The problem here is that your symmetric keys are not the same key, so it cannot be used in the destination database to decrypt the database on another database/instance/machine. Take a look at this link which describes the encryption hierarchy in SQL Server.

Basically, what is happening is you're creating a symmetric key on Source and using that to encrypt the column data. That symmetric key is protected (encrypted) by the certificate, the certificate is protected (encrypted) by the database master key and the DMK is protected (encrypted) by the service master key.

When you restore the DMK and Certificate to the destination database and create the new symmetric key, this doesn't allow you to decrypt the original data because the encryption was done by a different symmetric key.

In order to decrypt the data, you need to create an identical symmetric key. You achieve this by specifying the KEY_SOURCE and IDENTITY_VALUE properties of the symmetric key at creation time. By default, these values are randomly generated unless you specify explicit values.

By providing explicit values, an identical key is created and can be used on a different database/instance/machine to decrypt data encrypted by the source symmetric key. You can even use different certificates and database master keys to protect your destination symmetric key, it won't affect the decryption because the symmetric key is identical to the source key and once opened will decrypt the data.