Steps to reproduce:
- Take a blueprint book from your library
- Close blueprint library
- Shift-scroll to another blueprint in this blueprint book (with a different icon)
- Clear cursor
- Open blueprint library again
The icon of the blueprint book will have changed to the icon of the last blueprint you had selected but if you take the blueprint from the library again it will fall back to the first blueprint in the blueprint book. I would expect the blueprint book to either not change the icon or remember the last selected blueprint.
Other cases
Everything works as expected if you take the blueprint book from your inventory or your hotbar. It remembers wich blueprint you had selected last and changes the icon accordingly.