Photos error "PHPhotosErrorNoURLBookmark" not fixed after Repair Library - MigrationService Catalina

In addition to a small Photos library on my laptop, have 3 additional Photos libraries that live on an external thunderbolt drive. In August I started using a newer Mac with OS Catalina installed and was able to open and use the default library without issue, but this past weekend, I Option-opened another library for the first time, received the above error, and to repair. This happened with each external library. But after repairing, the library still would not open, saying "Photos was unable to open the library [library name]" (3135). Checking console, I see errors in the PhotosUpgrade log (see also screenshot) that include the following line: MigrationService.m:190 Failed to convert a bookmark to url. Error: Error Domain=com.apple.photos.error Code=46508 "(null)" How can I fix this?