While playing in the snapshots, I often had the problem that my Ctrl-key randomly got stuck, which caused problems like pressing "a" while writing in chat clears your whole text, trying to throw one item throws a whole stack, or hitting backspace clears the whole word instead of only one letter.
It took a while until I noticed that a combination of holding the AltGr-key and quickly moving my mouse was responsible for this problem. I also noticed that this happens more often when the game is lagging and not running smooth.

Steps to Reproduce:
1. Hold down AltGr and quickly move your mouse (moving my mouse in big circles worked the best for me)
2. Hold a stack of items and hit "q" once. If instead of one item the whole stack is thrown, it indicates that your Ctrl-key is stuck
3. If it didn't work, try moving your mouse quicker/ in bigger circles/ for a longer time or somehow create some lag while you move your mouse