How to remove someone from Play Store Internal Testers

A user was part of the 'Internal Test' group for the app on Play Store. They are not an internal tester any more. I have removed them from the list. They have confirmed that they've gone and clicked on the 'Leave' link on the join testers page.

However, even now, whenever they try to purchase anything in the app, they only get the test-card payment options (always approves or always declines) with 5min renewal cycle.

How can a user be removed / leave the internal test group so they can make 'real' in-app purchases?

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