I have 3 products grouped under one category. For example New Letter is a category and there are products in it, Free - free Subscription, Basic - paid 10$/month recurring, Premium - paid 15$/month recurring. Plan upgrades/downgrades are set as Upgrades: Free -> Basic - Default Rate Basic -> Premium - Default Rate Free -> Premium - Default Rate Downgrades: Basic -> Free - Default Rate Premium -> Free - Default Rate Premium -> Basic - Default Rate Upgrade plans are working correctly. But while downgrading For example Premium -> Basic, then again Basic->Premium - It ends up activating both Basic and Premium and while switching to FREE plan i get "This payment system could not handle zero-total invoices" and invoice gets created in pending state. How to handle it? I want the FREE to get activated. Is there a way to fix this issue?