So I started messing around with the 17w15a snapshot and I noticed that if you try and make a bed out of your recipe book, while in your normal inventory. NO CRAFTINGTABLE, that a plank will be placed on your head armor slot, and one in your body armor slot, see picture if not clear.

The way I found this is by adding a bed to my invetory (/give @p minecraft:bed). A recipe is unlocked, as the text in the top right corner shows, and froù then this bug occurs in the inventory system, if you try and make a bed when all the items are in your inventory thourgh the recipe book