Gocardless payment request issue (broken after update)

[vcavel]

There is an issue when creating a gocardless payment request after the custumer subscribed to the service.

What should happen :

• Gocardless payment request is created for this customer for the 1st time
• A gocardless subscription email is sent to the customer because no mandate exists
• Customer subscribes to gocardless, a mandate is created, payment is made
• Gocardless payment request is created for this customer for the 2nd time
• Payment is made automatically because a mandate exists, no subscription email is send

What happens :

• Gocardless payment request is created for this customer for the 1st time
• A gocardless subscription email is sent to the customer because no mandate exists
• Customer subscribes to gocardless, a mandate is created, payment is made
• Gocardless payment request is created for this customer for the 2nd time
• Payment is not made, a subscription email is sent again to the customer even though the mandate already exists

This bug only happens on new customers who subscribed after an ERPNext v15.xxx update (i don't know which one), there are no issues for the customers who's mandates are older than the update who broke this integration.

Ecommerce Integrations: v1.20.1 (main)
ERPNext: v15.27.1 (version-15)
Frappe Framework: v15.29.1 (version-15)