ES6 seems to only work some of the time. If I declare a function using the 'let' keyword, sometimes it will show up as undefined. Not sure why it only works some of the time. I have had instances where I will open an old repl.it session that allows ES6, copy and paste the exact same code, and it will work in one session but not the other. Please help me fix this issue. I want to keep using repl.it, but if this keeps happening, I think I will need to switch to another editor.