This issue is very hard to troubleshoot here but if this is only happening for one specific merchant my instinct would be that perhaps another app could be somehow interfering with this mutation or there is possibly something unique about this store (specific beta flags enabled) that is causing this. Do you know what store plan this store is on?
The customer had told me that he was using the normal “Shopify plan”.
However, the customer did not know where he could view the extensions and beta flags.
Can you show me where the customer can see this?
Unfortunately, we don’t have access to his Shopify account ourselves