I'm having problems with the Check Challenge on step 6, with regards to the Chatter Group.

I have created the Chatter group and a lightning page to support it. I have been getting this error for the last hour:


It's driving me nuts - I've tried everything, even renaming the page. It's quite clearly there.



Salesforce is this a bug?

I'm doing the simple lightning components challenge and have hit this problem in my existing trailhead org and a brand new dev org that I've just created:

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: QVWBQHAG