That's great because I was out of ideas.
As a side note, it's why I've moved away from using most built in variables and many of the specific event types. They often have unintended side effects because they do a lot of things automatically and behind the scenes. I'm not saying you should do that though as they provide a lot of benefit and ease of use as well. It's really just personal preference.
Here's how you would do roughly the same thing without built in variables:
Code:
///create event
hsp = 0;
vsp = 0;
spd = 10;
///how to set speed (replace in your current movement keys)
hsp = spd;
hsp = -spd;
vsp = spd;
vsp = -spd;
///how to stop movement
hsp = 0;
vsp = 0;
///step vent
x += hsp;
y += vsp;
There are other ways of course and lots of YouTube tutorials on it as well. See Friendly Cosmonaut or Shaun Spalding for example.