Inventory Slot Lock

In my Minecraft world, I found a geode and when I came back put the amethyst blocks back in my chest and then I went back, mined one more block and when I went to put it back in the chest I couldn't move it out of my inventory. I recorded it, but after the video I crafted a bucket and got some water and when I went to try and put it back I for some reason had two amethyst blocks instead of one and it let me move it this time. Also I would provide the video but it is too large.