I have a large library running on Windows 11. I also run the same library copied to a Linux Mint machine. The Linux version of Calibre reported quite a few issues with the library that didn't exist under Windows 11. So I ran a Database Restore on the Linux machine. This fixed all issues previously reported by Check Database, but it also reported 4 folders that were ignored. These 4 books were missing in the library (I guess that what it meant by "ignored"). Those 4 books exist in the portable drive I used to copy the library to the Linux machine. So I added the 4 books and everything works fine. However, when I run a Check Database, it reports the same 4 books as Extra Titles and wants me to delete them.
Why? What causes Calibre on Linux to ignore these 4 books during a Database Restore? I thought the library folder was cross-platform compatible: Linux, Mac, and Windows. There is nothing exceptional about these 4 books, very vanilla, no long filenames, etc...
