Object validation for intersection object

We have an intersection object between a custom object and account object. We have exposed this intersection object as a subtab on the custom object and we can add accounts on this intersection object. We have an object validation within this intersection object to check if 2 fields on this intersection object are required. Users try to add multiple accounts in the intersection object, usually more than 20. For each account added, an intersection object record will be created. When users try to update the 2 required fields, we see the validation shows up even before save. When we