I'm not familiar with this project, but I'll help if I can.
Can you help me to understand the problem you're having, please?
> ... it works at first, but then stops.
Do you mean the project stops?
Or the project is still running, but it's not doing what you expected / wanted?
> It adds the up/down/left code to the food sprite (without me doing anything)
When you say "It" - what is the "It" in this case?
What code is it adding?
Can you share an sb3 project file? or a screenshot? or a video recording of the code being added?
Do you mean you can't delete the code blocks?
How did you try to do that? What happened when you tried?
Anything you can share to let me understand what you're seeing would be a big help.
Kind regards
D