Sass editor is skipping/ignoring imported partial

Problem: Partials that are imported using the shorthand method of refering to the partial file, are being skipped / ignored by the editor.
Product / version: Rubymine 2.5 EAP 96.1146.

Test case (see the file 'test-case.scss' within the zip attached):

@import "subdirectory/ignored_partial";
@import "subdirectory/_partial.scss";

.problem{
    width: $ignored_variable;
}

.no-problem{
    width: $good_variable;
}

What is the expected output? What do you see instead?
The editor should recognise the variable '$ignored_variable'. Instead the editor says that it "cannot find variable '$ignored_variable'". 

Additional information:
In an attempt at trying to further isolate the problem, I found that when the file '_ignored_partial.scss' is moved so that it appears in the same directory as 'test-case.scss', then the variable '$ignored_variable' is recognised by the editor.