First boss bugged out. When his health reached 0 he stopped doing anything. After restarting from checkpoint I'm before the boss battle, but the passage is blocked, my map shows that there is a teleport after the boss, but it's inactive. Can't progress any further and it would suck if I replayed the whole thing just to have it happen again :/

Same thing. I've tried it on two different computers and with two independent walkthroughs. The game is very cool, but the first boss is unbeatable.

Reinstalling the game through GOG Galaxy helped. The bug seems to be present in standalone installers only.

Hi guys,
Sorry for the delay in replying and the inconvenience caused by this issue. We released an update that fixes this issue, it took a while to detect it because it only occurred on GOG and was related to achievements. If there is any problem with the save file after the update, please let us know that we can recover them.