press too many buttons

When you walk around in the world (both in multiplayer and singleplayer) and you press both tab and shift, and then press A (to go left) it doesn't work. any other direction works, except anything that has something to do with left (A). even though the player menu from the tab isn't in singleplayer, it still doesn't work to walk left. I have also tried to change the control to it, but it is still tab that does it. thanks for taking time to read this.