It's really hard to explain, but there's a problem with the game or my PC, where you have to click and hold items to move them, you can't shift-click items, and it's really weird. I didn't use to have this problem, but it's not the mouse as I have tried 3 different mouses…
Minecraft mouse/clicker bug?
Guest
Make sure you're not in touchscreen mode, I've had the same problem before and it was because I was accidentally I'm touchscreen mode.
Ducky