GE Adora Pulley or Warped Belt?

My drive belt came off the other day, so I opened up the back to put it back on and noticed the pulley was a little loose, so I tightened it up and re-attached the belt, but when I manually turn the pulley, the belt rides off the side nearest the tub. I replaced both belt and pulley about 8 months ago, and it worked great. But I’m hoping I don’t need to again. Any advice would be greatly appreciated. Cheers