There was an unexpected error while verifying this challenge. Usually this is due to some pre-existing configuration or code in the challenge Org. We recommend using a new Developer Edition (DE) to check this challenge. If you're using a new DE and seeing this error, please post to the developer forums and reference error id: OVSPKDKP

https://developer.salesforce.com/trailhead/lightning_components/lightning_components_expressions

Hi Guys,

I have been trying to complete the Lightning component: Using Expressions trailhead and I keep getting the error "Challenge not yet complete... here's what's wrong: 
There was an unexpected error while verifying this challenge. Usually this is due to some pre-existing configuration or code in the challenge Org. We recommend using a new Developer Edition (DE) to check this challenge. If you're using a new DE and seeing this error, please post to the developer forums and reference error id: XUDHMECE"

I have now set-up 3 developer orgs and get the same error for each one. ANyone have any advice? 

Thanks
Liam