Even though these special sites might be backed up error-free, there might be features and configurations that could not be retrieved.
These special sites should not be attempted to be restored.
Office 365 Video Portal - This is a site for hosting Office 365 videos. It cannot be backed up or restored using SharePoint backup/restore feature. It works in conjunction with other systems like Azure media services etc.
Community features - This is a default site created by SharePoint and acts as a template for community related features. Any community site that users create, this site provides all the community related features. This site should not be restored as it can cause issues with community sites.
This is one of the components for creating custom apps in SharePoint. It works with other Office 365 systems in conjunction. It cannot be backed up or restored independently.
This is the default site for project web access. This should not be backed up and restored independently as it works with Microsoft Project server and may cause issues with Microsoft Projects.