When placing lily pads, very rarely, I've placed two lily pads while only expending one from my inventory. Note: It is not that I placed two separate pads, and the second one didn't reduce the number of pads in my inventory, it is that when I've gone to place one, an extra one has appeared next to it. When the second pad is broken, it acts as normal and gave me an extra lily pad I did not have before. I saw it happen once, went into a creative world and tried to recreate it with the same conditions (switched to survival mode for the tests) with no success. I'm posting this now because it just happened again in my survival world.