Problem with importing ebook chapters

I’m trying to import an ebook in German with chapters that are more than 2000 words long. It says it will be split into several parts and the other parts will follow shortly. The 1st part does show up, but the other ones never appear. This means that I can’t continue importing chapters, since I might have to do it all over again anyways, and I also can’t start reading the ebook, since huge chunks of the chapters are missing.

I’ve imported plenty of ebooks before and usually it’s not really an issue, since the other parts show up pretty quickly. However, now they won’t and it’s really hindering my learning schedule for today.

Here are the chapters I’m trying to import:

I’m using Google Chrome.
I tried Firefox as well but there it just gives me a time-out error.

I see lot of lessons were imported into that course today. You have 139 lessons there.
Can you please look again?