Clients attempting to create new mandates via the GoCardless payment gateway module may encounter an Invalid filename for redirect error (an Oops error).

The format for some data that GoCardless returns when creating a new mandate has been changed. This causes WHMCS's data integrity validation to fail.

We have created a hotfix for WHMCS 8.5.1 to accept the new GoCardless URL schema. You can download it at:

https://whmcs.community/files/file/179-module-7849-gocardless-oops-error-on-mandate-creation/