when you craft armor and go to the place where you put armor on, and when you put the armor on for example the helmet. You make a diamond helmet and put it on and then make a gold helmet and then click on the gold helmet in the armor section it will replace the diamond helmet and you will loose the diamond helmet for good unless you make another one.

Steps to Reproduce
1. Make any type of armor
2. put the armor on
3. place another peice of armor on top of an existing armor.