Not sure if others have had this problem, but I finally managed to complete this game while also obtaining the Chronoscepter, but only 2 achievements actually recorded.

The only achievements that my game+GoG Galaxy recorded are the Mantis and Longhunter boss fighters. However, I should have every achievement except possibly treasure hunter.

GoG devs, any updates on this?

Half of the achievements are glitched for me, but I noticed that 3 of the 4 are uncommon and one is legendary at 0.0, so I'm guessing nearly everyone has had this problem?

All achievements triggered on my first playthrough, except the Treasure Hunter (which is bugged for sure). Went through the game a second time, just to make sure that I didn't miss anything.