That was the bug. A trivial example would be a bug that replaces the configuration for all customers with the last uploaded. Then when the next customer upload

That was the bug. A trivial example would be a bug that replaces the configuration for all customers with the last uploaded. Then when the next customer uploads a new (valid!) config, you have a problem. Obviously it wasn’t that trivial but the point is: it wasn’t the customer’s configuration change that was the problem but some code that managed the config change.