Synchronizing all configurations causes a PHP error

I was following the steps to set up the REST server:

1. Enabled rest module.
2. Added rest.settings.yml at sites/default/files/config_somehash/staging/rest.settings.yml as per the above guide.
3. Open admin/config/development/sync and hit Sync all.

The following error raises:

The entity that is not found and causes the error has $name as entity.display.custom_block.basic.default con and $id as custom_block.basic.default