I'm getting the same error!

If I ask for "openid email profile accounting.transactions accounting.settings offline_access" it works.

...but if I add accounting.contacts to that list, I get sent to this page:

 **Sorry, something went wrong**  
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 If the issue continues, please visit our Status page  
 Error: unauthorized_client  
 Invalid scope for client  
 Error code: 500

I've tried in multiple browsers on multiple computers and always get the same behaviour. Asking for "accounting.contacts" breaks it.

What's strange is we have 2 xero apps, a test one and a production one. The test one lets me connect with the accounting.contacts scope, but the production one does not.

Did you ever find a solution to the problem?