Not sure if it's worth bumping this for such a simple solution, but...
The problems is just that when you are holding left/right and then press up or down your sprite's angle doesn't change to match the new direction, so just add "if key left arrow is down" and
"if key down arrow is down", set sprite's angle to 90 (do the same with the right arrow). And then "if key left arrow is down" and
"if key up arrow is down" set sprite's angle to 270 (again, the same for the right arrow).
Quick and embarassingly easy. Sorry for bugging you about it, Ashley.