I am trying to execute this query:

x => x.SearchParent().Match(CurrentPage.SearchFolder)

But I am getting back a 400 from find with exception NumberFormatException.

Here us the defination for SearchParent()

public static string[] SearchParent(this UnifiedFile file)

Result in Find index:

"SearchParent": [
    "/PageFiles/",
    "/PageFiles/112971/"
  ]

 Also have this:

client.Conventions.ForInstancesOf().IncludeField(f => f.SearchParent());

Cannot see why a tring needs to be converted to a number, while matching a string...