I wasn't really looking for problems, it's just something I noticed very quickly. Bad luck then I guess. Upon further testing, it does only happen with certain window sizes indeed.

But it's a typical example why front end development with web technologies still isn't where it should it be.

And I'm not blaming the front end devs, the technology just isn't up to the task. The fact alone that you have to deal with problems like this is telling enough.