Photos and Favorites

[yetanotherguy]

I am using the .63 build on my Lumia 930. I like my photos tile to show me pictures that I mark a favorite. On trying to set up the new WM10 installation, I noticed that even for the files that are stored locally (downloaded from somewhere), I am unable to set _some_ pictures as favorite. The criteria for being able to favorite or not does not seem to be clear to me (example, two pictures that I downloaded from my oneDrive account to saved pictures - one can be favorited, the other cannot - both are pretty high resolution). Can anyone shine any light on this? Do you see the same thing affecting your pictures?

Thanks