An update on this post. I got a response from another website [https://www.macscripter.net/t/index-of-an-item-in-an-applescript-list/74205). The results from the "repeat with -- in" is a reference to the item not the actual item. Hence, the code should be getPositionOfItemInList(contents of selectedNAS, NAS_Names)

I thought this problem was new. Open your original workflow, then create a new file (File>New) as an Application. Copy and paste your original workflow into your new file and save it as an application. It should now work.