TFS 2015 Test Upgrade Issue (from TFS 2013.3)

Where should we be posting issues with TFS 2015 RC?

I did a test upgrade (from TFS 2013.3) and it failed with the following error:

[2015-05-20 00:25:28Z][Error] TF401257: An error occurred migrating data to the new schema. An error occurred inserting data to table: dbo.tbl_WorkItemCustomWere.  Error: Cannot insert duplicate key row in object 'dbo.tbl_WorkItemCustomWere' with unique index 'PK_tbl_WorkItemCustomWere'. The duplicate key value is (1, 80024, 10246, Mar 16 2010 11:05PM).
The statement has been terminated.

Thanks

Scott