Variables in a programming language can have any valid name. Names only help you to remember what they do. So, when your animation does not work when you changed a variable name, there's certainly a bug. Try to find it and fix it. Most likely you used variables of the same name somewhere else. If you can't find it, use the debugger to look what's happening in your animation function. There's a debugger workshop in the tutorial.

You posted your problem in the wrong forum. "Bug Hunt" is for bugs in the software only, not for bugs in your script.