Reported in the forums:

I have found a bug in the shipping bin (tested in singleplayer 1.3beta)
You can duplicate items that you put in the shipping bin
If you right click on them to get 1 item back, you can do that endless for a item that only has a stack of 1 in the shipping bin, you will get 1 item in your inventory for every right click you do and the item in the shipping bin will still be there

Fixed in develop for the upcoming Chests Anywhere 1.10-beta.3.