6.11.4 is a very old version (over 2 years old) and should be updated. 6.40.5 is the latest version. Although I doubt this is the cause, I don't know what else could be causing it besides something in the script. You can check the code by using the find feature. Someone else will have to help you with this, however, I've run out of ideas and I have no experience with joysticks and hardly anything with movement.

"You level up the fastest and easiest if you do things at your own level and no higher or lower" - useful tip My 2D game - release on Jun 13th; My tutorials