magento 1 associated products not showing when adding child products

Hi We have a magento 1 store, ver. 1.9.4.3 We have succesfully set up many configurable and grouped products in the past but recently we have found that some child products are not showing in the assosictaed products tab grid of the parent products. For configurable products, all child products have the relevant attribute asigned and all products are unable the same attribute group. We have repaired, indexed and cleared cache. The products an enabled, assigned to the same website and in stock. The products that are not showing have previously been assigned to grouped products, and when we look at those grouped products, the problem child products are not showing in the associated products grid, but if we look directly at the database with tbe below query we can see that are associated. select parent.type_id as parent_product_type, [login to view URL] as parent_sk, child.type_id as child_product_type, [login to view URL] child_sku from rr_catalog_product_entity as parent join rr_catalog_product_relation as link on link.parent_id = parent.entity_id join rr_catalog_product_entity as child on child.entity_id = link.child_id ORDER BY `parent_sk` DESC limit 100000 We need assistance on fixing this issue so we can assign the child products accordingly. Examples and dec site access will be provided and we will need to know how to replicate the fix on our live site. thanks