Missing one record in solr streaming expressions

It's a simple use case, i have two collections products and related products, product_id_l is a unique key in products collection and reference field in related products collection, please find sample documents below.
 
product:

{  "id":"12345", "id_l":12345, "product_name":"product1", "related_product_count_l":2 }

 
related products:

{   "id":"56789",   "id_l":56789,   "main_product_id_l":12345,   "product_name":"product10"   "relation_type_code_i":4 }

,

{   "id":"98765",   "id_l":98765,   "main_product_id_l":12345,   "product_name":"product11"   "relation_type_code_i":2 }

 
gatherNodes(relatedproduct, search(product,q="related_product_count_l:[1 TO *]", fl="id_l",  qt="/export", sort="id_l desc"),  walk=id_l-> main_product_id_l, gather="related_product_id_l", fq="relation_type_code_i:4",scatter="leaves, branches")

 
I am trying to fetch all products which are having more than one related products then joining with related products collection to get all related products then filtering relation type 4 ones.