There seems to ba an issue with one or two achievements.

First, collecting all backpacks "Your favorite backpack" seems to be broken because although quite easy to get, the rate is "legendary 0%".

Second, I got one secret achievement locked after completing everything. On Steam, a few broken acievments were removed and when comparing mine to the list on Steam, I got every single one. So this last secret one, I can't tell which one it is, seems to be unobtainable as of the current game.

EDIT: The second one is "radiating love", an achievement which got deleted on Steam because the required radio is missing in the game. This is fixable by downgrading to 1.5 (the 1.9 savegame works!), then you can find the radio. The other achievment however is not fixed.