Just chiming in to say that I am having the same issue as well. It also extends appears to extend to GOG Galaxy as well. I normally sort my games alphabetically, but each reload is jumbling the games around. Weird.
So is it merely moving the games around in the library, not missing pictures/links to some games? I guess that would explain why the "missing" game can still be located with the search. It was hard for me to tell if a game was "missing" as I have so many games, so if I didn't see 1954 Alcatraz as the first entry, I presumed it is not listed at all.
EDIT: Yes indeedy, I could e.g. now see 1945 much later in the list (at place #90), when it should be as the first entry. Some other games were also in places where they shouldn't clearly be alphabetically,
Odd. Is this a new bug, or only noticed now? I haven't really paid attention as I normally just download my games with gogrepo.