Something went wrong while saving this configuration: Area is already set
This is a known Magento issue that has surfaced in Magento 2.2.4 and continued in Magento 2.2.5, unrelated to our products. An official fix is expected to be included in Magento 2.2.6.
The official patch already released and is available at the link below:
This patch provides a fix for problems that merchants experienced when trying to change a storefront’s applied theme in Magento 2.2.4 or 2.2.5. See GitHub-14968 for more information. Merchants who are running Magento 2.2.4 should upgrade to 2.2.5 and then apply this patch. Merchants who are running 2.2.5 should apply this patch or upgrade to 2.2.6 when it becomes available.