Achievements bugs ?!?!

[Magos]

I finished the game first completing all but 2 achievements - The gnome and save-all-buildings-from-striders. Later after playing through it a second time I also completed the latter achievement, however 2 of my earlier achievements wree gone (kill-combine-with-grenade and kill-hunter-with-fleshette). I restarted the game and now another 2-3 achievements have disappeared (been locked again). What is going on? What kind of bug is this????

 

[PortalStormzzzz]

I think it has to be on the same saved game or something. I beat the chopper one, got it unlocked, went back and it was gone, reloaded it from post-chopper, and it was unlocked again.