Hi Stephane,
The files are offered through WebDav, which should allow you to use download clients other than your web browser, which may be more fault tolerant. I would try WinSCP, which I just did myself. I found that I was able to start from the web page using right-click > Copy Link Address, and then bring up WinSCP, select a New Site and paste in the link address. That put the full link into WinSCP, showing me only skyline.ms as the "Host name". When I clicked the "Advanced" button and then selected "Directories" the rest of the directory location was listed as:

/_webdav/home/software/Skyline/events/2018 Webinars/Webinar 17/@files/Webinar17_data.zip

If I just connected like this, I got a 400 error that the directory Webinar17_data.zip could not be found, but if I clicked through that I could eventually navigate up to the parent directory. However, if I edit the path to remove the .zip file, then I could get there the first time without error.

From there I could easily initiate the download. I did have to sign in, despite the directory being open to anyone for reading, but I signed in with a normal user account, and that worked just fine.

I hope this can help you. There are many WebDAV clients, but I use WinSCP for other types of file transfer and it also supports WebDAV. Let me know how it goes.

--Brendan