Exporting catalog "Photos could not be found"

Community Beginner ,

I work as a photo editor. My clients only send me Lightroom Classic smart preview catalogs. I do NOT have access to the raw images. Recently on the last few catalogs that I've exported i've been getting an error saying "Lightroom was able to successfully export some of the images assets to the new catalog, But encountered these problems" "Photos could not be found" Photo below to show you what i'm talking about. I've never had thsi problem before. will it cause issues for my clients when they go to import the catalog back into their own, where their raws are located?