First off, spoilers ahead if you have not beaten TFTD. Turn back now!
I have encountered an issue with the final level of the last mission in TFTD, namely the third level where you assault the Alien Horror. In the original game, the level was a large spiral, that you had to work your way around, before finally making it to the tomb chamber in the center of the map.
I got to this level in T'leth in OpenXcom TFTD, and imagine my surprise when I found a door leading to the Alien Horror immediately off the access lift at the start of the level. See the linked image. All it took was 2 MC attacks and a 2 disruptor launcher shots to defeat the level. On the very first turn no less. I am assuming this is some kind of bug with the terrain placement and that opening is not supposed to be there?
Or did I miss something REALLY obvious on my play through of the original game?
image can be found here:
https://i.imgur.com/lShD3MH.png