When trying to place a piece one space away from a wall -- experienced tetr.io players will use finesse techniques like "hold left, tap right" to play quickly using DAS (Delayed Auto Shift)
In this game, left and right DAS appear to interfere with each other, so "hold left, tap right" will move the piece several spaces away from the wall as DAS remains active, even when moving in the opposite direction
It is a minor hangup but makes the later levels more frustrating, when you're trying to play quickly!