Duplicating Private Channel SharePoint sites?

Thought I'd ask here - have a strange one for you.

My Business Premium tenant (targeted release)- I create a team, then I create a private channel. If I click on the 'files' tab, it says it can't find it. So I wait.

I can see that the SharePoint site -----/sites/teamname-channelname is created correctly, with the document library ready to receive documents.

However, when I click on the Files tab in Teams, besides giving me the error, it creates a second SharePoint site, /sites/teamname-channelname# where the # is a random number. No matter how long I wait, I always get a new SharePoint site.

Do you know of anything I can look at before I put in a ticket? All my policies and settings for Teams/SharePoint allow private channels. 

My work E3 tenant works correctly.