Placing a book on a lectern and removing it causes the book not to stack except with other books which have also been placed and removed from a lectern.

Steps to Reproduce

1. Sign a book and make several copies of it.
2. Place one of the copies on a lectern.
3. Remove the book.

Expected Behavior
The removed book will stack with the other copies.

Actual Behavior
The removed book does not stack with the other copies.