`COUNT()` function returns random values ocassionally

Hello,

If there is an error in my query, please let me know. Our internal ERP software runs this query to fetch a list of all SKUs shared between our two companies, and uses `COUNT(CASE)` functions to get the the count of rows in the inventory table of both companies.

Pastebin to Query

The issue comes up the first 27 SKUs return quantity perfectly, and then from there the in stock quantity for both companies get seemingly multiplied by itself 2 or 3 times randomly . If needed, I can potentially provide a mariadbdump for both companies inventory tables (in different databases) and the central products table.