If you are running (not walking) and still have the same problem, you may have triggered some weird bug I haven't seen before

Sorry for the late reply but I have not got here since then.
Well, after my post I contacted the support and they kindly replied that my savegame was corrupted and even offered a correct savegame at the same point in the game.

Hi all,

I had this glitch yesterday, then today after work, I started a new game and the plank glitch didn't happened to me this time, but I did something different between the 2 games.

At the beginning of the game, you get a red token from a bottle that you must break and in the first game, I didn't used on the piano in the saloon (on the right side from the entrance). Using the token on the piano will play a small movie and you will get the oil lamp too.

I got the oil lamp anyway somehow when I went down the trapdoor. However, the plank glitch happened to me later on the first game.

On the second game (today), I used the token on the piano, watched the small movie and got the oil lamp that way. At the jump the plank part, Edward jumped from it without any issues.

Before the second game, I also installed the french version of AITD3 (from CD) with DOSBox v0.74-3 (latest version) and I did the above steps (token on piano, watched the movie and got the lamp) and the jump was fine too with that version too.

So if you got the glitch, try these steps on a new save (just for the test) and let me know if it worked for you. It worked for me.

I finished the game a few days later by restarting it and doimg multiple saves along the game.
I don't rember if tha happened again tho.

Just to narrow down a bit more the issue, I'll explain my case:

I was happily playing, not having done the piano token and video, until I arrived to the dynamite hole and the guy shooting through the door.

I hurried to light the dynamite but couldn't exit on time before it exploded - it got me while opening the door or something. Edward went to the floor like usual but I didn't get kill. He just stood up and I could keep playing. However, the bug was on place and I could walk through the air and pick up the bird statue, and afterwards he wouldn't jump the plank.

I highlighted that part in particular because I could continue with a lucky save that I had just after the Hangman, exactly before the dynamite part. Doing it as it should (opening the door after the gunman, placing the dynamite, lighting it and running out to be protected of the explosion) the bug didn't happen this time.