I have a big problem in chapter 16, which I haven´t found yet.
I´ve fed the brain machine and searched the dead warriorer, but I can´t reach the arch, because the platform didn´t come down after fedding the machine.
Maybe I have to do something I missed earlier ?
I looked at the scene in a lets play and it looked different. The plattforms simply don´t move.

Then it's probably a bug. The platforms should lower as soon as the demon appear; you can even run into the arch and flee the combat (and get a very interesting scene with Rebecca later if you fail to loot the scroll from the demon). Have you tried reloading the game a couple of times?

I reloaded the game and also played the whole chapter again from an earlier point, but there is no difference.
The plattform at the top, where the monster appears, moves , but I can´t climb the outer rings to the middle.

Hello again, my third attempt (I replayed a much earlier save) solved the problem.
On my first two attempts I managed to leave the plattform at the beginning without going up (the place remaind even).
Only after filling the fifth brain the plattforms went up. Maybe this could have caused the problem.
I´m in no mood to test it again now. Maybe anybody wants. Good Fun.

It's the worst level in the game, I can't blame you for not testing further. ;) Anyway, it may be worthwhile to wait up to a minute before performing any action, especially concerning the brain machine, so that the platforms can fully extend/retract.

I'm glad you managed to work this nasty segment out yourself, otherwise I would've suggested to download one of these save games as a last (however objectionable) resort. I hope you enjoy the rest of the game, especially that delightful puzzle marathon! (^_~)

I played the game to the end. Normally I play adventure games, so the "puzzle marathon" was a highlight of the game and I didn´t need much time at this point. The mirror room was a bit annoying, because it did take some time, before I realized that I allready solved it.
Games like this I do not play very often. Thank you GoG for this special offer, because otherwise I wouldn`t bought it.
It´s a great fantastic game, despite the brain machine.
My english isn´t good enough to describe the atmosphere of the game.