If you have a trowel in your offhand, and have let's say some cobblestone, diorite, and granite in your hotbar, and you're holding andesite, the andesite will place first and then the trowel will pick one of those blocks from your hotbar to place down, excluding andesite (the item in your hand)
I suspect this could be an incompatibility with the client-side mod Accurate Block Placement, but I am unsure as I have not tested without it.