Issue: The problem is the index itself. Apple, in its wisdom, has decided that instead of actually searching on drives for what is really there, Spotlight will create an index and search the index.

There are instructions out on the web on how to make spotlight index the network locations, but the simplest solution is to use a 3rd party app/tool to do the file search.

EasyFind is here: https://www.devontechnologies.com/download/products.html  under Freeware section or it can be downloaded from iTunes.