This is beyond weird. I thought for sure there was something wrong with data model expression, you were using the wrong field in the pie, or some other accidental mistake to explain the issue; but everything looks correct (except the pie chart).
Can you please open a support case and ask them to include me in a webex session to take a look? Please note that I will not be available until the end of the week, so it might be a few days before they can arrange that call.
Thanks,
Gregg