GUI Bug

*What I expected to happen was: Clicking the block and shift+click, like every other day

*What actually happened was: I couldn't do that anymore. I need to drag the item while clicking it. That's the only way I can move any kind of items in my GUI space (e.g. furnace, inventory, chests)

*Steps to Reproduce: Honestly, it's been two months, I can't really remember exactly how I triggered it. I didn't even know what happened. I just went on, something happened and I crashed. Then I couldn't click like I normally do anymore.

I have real trouble with moving the items in my inventory. Or any GUI space. I can't [shift+click] anymore. Instead, I need to click and drag the item across to my inventory – the only way an item can move – creating major annoyance, delay, and inconvenience. This also means that I can't enjoy my Minecraft experience fully. I already sent a message before, but your staff said you couldn't help me. I'm sending another message to you. I hope this time maybe something could be done to solve the problem I've been having for at least 2 months. Thanks and I hope to hear from you soon.