When I play Cultris 2, it doesn't seem to recognize keystrokes I make unless I play very slowly. When I am playing at a relatively fast speed, the piece does not hard drop when I press the key and I may have to hit it two or three times for it to work. Other times, it hard drops but not where I want it to. I have this issue with spinning the tetrimono too. It doesn't always register my keystrokes to spin the piece causing me to hard drop a tetrimono improperly or causes me to press the key to spin it a few times. This same issue can happen when trying to go left or right. What can I do about this? I don't have this issue when I play TOP or Nullpomino. These issues occurred when using my previous keyboard as they do now on my new one so it can't be a hardware issue relating to my keyboard. The only temporary fix for this is uninstalling and then reinstalling Cultris 2 every time I want to play which is burdensome since not doing that will cause all these keystroke recognition issues.
You are probably the one who asked that question on reddit some days ago. I didn't reply because I didn't know what to say. Your issue is weird because Cultris 2 is an event-based game, so every keystroke is registered (in contrast to NullpoMino). There's some anti-cheat code which randomly ignores some of your inputs, if the game thinks you cheat - but humans shouldn't trigger it (you need to do 2 Left or Right keystrokes within around 15 miliseconds - impossibru).
I don't know how to fix your problem. If you play on a newer Windows system, then try to disable Aero/desktop composition.
I disabled the aero desktop and I switched to using windows xp service pack 2 in compatibility mode and now it works fine.
Thanks for linking that video. The thread within the description was useful too.