I cases of some recent games, the review ratings seem to reset to "0 out of 0 people found this helpful".
I kind of negates the whole "community" aspect of the site, when it comes to the reviews and I'd be really happy to see this fixed!
(I even wrote to the support but to no avail).

It is a known bug, exists over one month.
GOG does not fix it yet, and GOG staff never said anything about it.
https://www.gog.com/forum/general/whats_going_on_with_frostpunk_reviews_on_gog_oo
https://www.gog.com/forum/general/the_what_did_just_break_thread_20/post1551

So I'm not the one gonig crazy at least :)
That's pretty lame from GOG, but I'm hope they'll eventually address it then.
Anyway, this is a great opportunity not to buy anything until this is fixed.

No, you are not going crazy and yes, it's happening each 2-3 days in some recent games. See Battletech, for instance, i had lost about 250 votes in my review less than a week since the release, and it's still resetting again and again.

I wrote a ticket and got no answer about it being a bug or not. Just silence, but they know it for sure.