There are a few errors I've noticed with the WASD commands, I assume this is a game issue but it may be a client one, I'm not entirely sure. The most prevalent ones I've noticed are if you're walking while you consume something, or sometimes just for no reason at all, it'll glitch and it'll make you continue walking in the direction that you had previously been walking. For instance, if I eat a mushroom while holding A, he'll continue to walk even once I've stopped holding A. The only  fix I've noticed for this is to hit the directional key again in the same direction, and it unsticks itself. This has forced me to walk through water unintentionally and lose all of my items, but that was partially my fault anyway for having swimming turned on.