Pictures missing in my Photo Stream on Windows PC

iCloud and Photo Stream are great tools to transfer pictures from, e.g., an iPhone to, e.g., a Windows PC. However, some pictures are not transferred, and I'm trying to understand why, and whether I can do something to avoid it from happening again.

Specifically, the pictures have been uploaded to iCloud,from my iPhone 6, automatically, just like they should. I know this because I can see them on my iCloud webpage (which syncs with my phone, just like it should).

Then, some pictures fail to take the step from iCloud to the Photo Stream on my PC. Notably, only some.

Given this situation, I downloaded thosePictures manually from iCloud (i.e., the web page) to my PC. It works fine, EXCEPT I could not figure out how to download them all at once, without being asked how to deal with each one.

So - second question - is there a way to batch download Pictures from the iCloud web page (on a PC).

Regards

Lars

Iphone 6, iOS 8.1, Windows 8.1.