What is your plan duration and price for the subscription that got billed twice? Are you using a "By Calendar" duration? Were they actually billed twice or did CBSubs report the payment twice? Have you reviewed the subscription at Stripe to see its billing cycle to see why it would bill twice? CBSubs itself doesn't issue the billing, but it's possible the subscription created incorrectly at Stripe.

Was the subscription billed 10 times (verify this at Stripe) or the payment processed 10 times at CBSubs?

If just processed 10 times at CBSubs it sounds like duplicate webhooks might be arriving, but it shouldn't be processing the duplicates as we use idempotency and lock times for baskets. Do you have multiple webhooks configured at Stripe pointing to the same domain?

If actually charged 10 times there's something very wrong at Stripe for their recurring subscription. Within Stripe on the left once logged in and viewing the dashboard click Billing then under the Billing heading click Subscriptions and review their subscription billing. A simple 1 year duration plan should absolutely not be having problems like this.

Have retested recurring billing using your duration and price and am not seeing any issues with the subscription or billing cycle behavior at Stripe or in CBSubs. Have reviewed API change log and there hasn't been any breaking changes after the version we use. Simulation of up to 3 years of renewals all seam fine. So I'm not sure how this could've gone wrong.

If you PM backend super user login credentials and include the username of the user affected I can take a look at CBSubs logs, but it's sounding like the subscription is duplicated at Stripe somehow.