How should i fit a drive belt for Miele w842?

The drive belt on my washing machine failed a month ago and I fitted another, supplied by Miele. It seemed a simple and worked fine till now. I located the elastic belt on the ribbed motor wheel and turned it onto the larger drum wheel. Now the belt seems to be slipping - drum starts but fails to rotate when full accompanied by a faint smell of burnt rubber.

I plan to remove and replace the belt before it fails again and I assume I fitted it wrong but can anyone tell me what I did wrong?

Thanks

jim