Placed two damaged bows in my small crafting area. Hit shift as I collected the repaired bow and all available inventory spaces filled with copies of the repaired bow. I placed them in a chest, logged off, exited game and reloaded. They were still there.

The bows were un-enchanted and the resulting bows were not fully repaired.

I replicated the error with two more bows in the same manner. (this time to fully repaired bows.)

The image was taken after I closed and refreshed my inventory.