Translations don't get imported in sub-layers in some cases

We noticed that text in some sub-layers of one of our Storyline projects did not get imported from the translated Word document. I decided to create a very small single-slide course for testing. In the attached zip, you will find:

• test.story - the original English course
• test.doc - a "translated" export from test.story (all I did was add Xxx at the beginning of each string.)
• test.xlf - a "translated" export from test.story (all I did was add Xxx at the beginning of each target string.)
• test_Word_Imported.story - The project with test.doc imported.
• test_XLIFF_Imported.story - The project with test.xlf imported.

Notice how the text in the two sub-layers remains untranslated.

I use Storyline 360 v.3.9.13567.0

This is a pretty big deal, as we provide localization services, and this adds a lot of copy/paste work. (Imagine doing 10+ languages and having 30+ items not get imported.) We have seen this in many other projects as well.