I just completed the following test:
I initiated an offline payment of a test user account, triggered the pay button in the basket, processed the payment and then subsequently cancelled the payment.
When I logged back in the "renew now" button, now shows the correct date!
very strange!
I wonder what would happen if I deactivate and reactivate an account - will the correct renewal period surface?
UPDATE: I unsubscribed and reactivated accounts (in the backend) and the renew now button is showing the correct date - Looks like this might be my workaround!!