A bit more than two months ago I did hear from several people having issues with our Hands-On Lab environment. And it became clear that only those who use Oracle Virtual Box 5 see such errors.
Then I read Danny Bryant‘s blog post (thanks to Deiby Gomez for pointing me to it) about similar issues and a potential solution yesterday:
And interestingly one of my colleagues, our PL/SQL product manager Bryn Llewellyn started an email thread and a test internally yesterday as well.