enchanting table and carpets

This bug shouldnt be too difficult. I have an enchanting table in my base. It has always blessed me with awesome enchants. Recently however i noticed that much enchants were getting bad. took some time before i noticed that the carpets i had put down between my bookshelfs and my enchanting table were not throwing letters at the enchanting table anymore. I removed the carpets "blocking" the path for the letters and they resumed going to the book again.