I played many games on my laptop, from Steam, Epic, and of course GOG. I noticed a weird pattern concerning achievements here. When I play a game I never played (Daymare 1998 for example) achievements work perfectly. But for the ones I have played on this laptop years ago like Metro Last Light and Prey, there are several buggy achievements. Sometimes they require the game and GOG to be restarted. At least Metro had a sign it won't unlock, with the overlay achievement not appearing. Prey's appear, but it still bugs out.

My question is, is there really a connection between buggy achievements and having save files from another version? Or is just Prey's achievement triggers really buggy?

Like I said in your other thread, there's nothing wrong with the achievements for Prey Digital Deluxe Edition. That's the base game plus the Mooncrash DLC. The game was never updated on GOG, so it's not like they broke something after I finished it.

I've seen reports of problems with the Metro games, but these came from someone using the discontinued GOG Galaxy 1.2, so I take them with a grain of salt.

As for having previous saves, the game may have recorded that you performed a specific action already, so no achievement triggers when you do it again. It depends on the game. Some might even unlock achievements the moment you start with an old save.

The list of broken achievements thread may be a better place to ask these questions.

Honestly, I thought about this, but this doesn't seem the case. Yesterday I was able to unlock several achievements, both from my old saves, and from my new playthrough (I reset my 3rd save slot). How did it work? I just closed the game, re-opened, installed a human power (after several tries) hoping for it to unlock, and it did. I think its more of a Galaxy issue than the game itself, but idk really.

GOG has many Achievements that are buggy and/or entirely non-working, and which would be equally buggy and non-working (or they only work for some people, but not others), regardless of whether or not you are using a save from another version of the game.

Whether or not using a save from another version adds a further amount of non-working bugginess, I do not know, it's possible though.

I couldn't get an Achievement to unlock for Metro 2033 Redux even though I tried dozens of times and it definitely should have unlocked. And when I complained about it in the Broken Achievements thread, another person said they have the same problem with being unable to unlock that Achievement.

I had never played any version of that game other than the latest version that is available on GOG.

On the other hand, another customer posted a screenshot of him having unlocked that same Galaxy Achievement, using the same exact version of the game that we (those for whom it does not work) were using.

And for some games, like Outlast 2 and Mark of the Ninja: Remastered, I cannot get any Galaxy Achievements to unlock at all, even though I beat those games and I met the requirements for unlocking several of the Achievements for each. I have also tried many things to make my Mark of the Ninja: Remastered Achievements finally start working, like verifying the installation, re-installing the game, etc. and none of that made any difference.

For Outlast 2, AFAIK all other GOG customers have also said they cannot get any Galaxy Achievements to unlock for them either, so for that game they seem to be universally bugged.

I've also experienced bugged Achievements in other games, like Death End Re;Quest 1, where most of the Achievements work for me, but some don't, like the one you get for beating the optional Pain Area Dungeon, which I've re-beaten many different times just to try to unlock the Achievement, but yet it never unlocks for me. And the Achievement for clearing Chapter 3 also didn't unlock for me even though I have definitely done that.

GOG's achievement system is a bigger afterthought than Nintendo's version of an achievement system which at the very least executes on the lines correctly.

I can tell you it has nothing to do with versions, the IDs of the game and achievements remain the same, so does the network communication.

But the system certainly has it's flaws.
I encountered a few games (for example Terminator Resistance and Monster Boy), where some achievements register and some don't.
While I can get a "completed the game" achievement, I am still missing the one for updating my first weapon of finding my first life upgrade (when I actually found them all).

I seem to have found a (probably temporary) workaround. I decided to verify/repair my Prey from Galaxy, took a while but not too long. After that, achievements work perfectly again. Idk if its permanent or if I have to repair every once in a while, but let's see.

Update: Finished the game. Ever since I repaired through Galaxy, achievements unlock normally almost all the time. There's 2 or 3 times they didn't, but exiting game and replaying it unlocks it.