OK, I think I know what is going on.
- The root cause is a tag, Science Fiction, had its case changed. I think that 'Fiction' became 'fiction'. This means that the folder on Android no longer has the right name.
- Folder names in Android can be case sensitive, so sometimes the case change doesn't matter but sometimes it does.
- You are not using CC templates, so none of CC's processing to detect case changing is being applied.
- Your device is apparently using a case-insensitive file system. This means that when you send a book starting with "!Science fiction", Android will happily use the folder "!Science Fiction" without changing its case.
- You have the setting Settings / Connecting to calibre / Wireless device connection / Scan on connect checked. This tells CC to check for books on the device that are not in the database. Because the case of the database file name is different from the case of the actual file name, the file name comparison is failing and CC is reporting new books with the different name.
The first thing to try is to turn off Scan on connect. I think that will fix it. If you are happy leaving it off then we are done. If, however, you want to use scanning then you will need to switch to CC templates. We can discuss this later if we need to.
Another possibility is to correct the case of the "Science fiction" tag back to "Science Fiction".