I've run into one bug at the end of Discworld, but I'm uncertain if it's a game bug or a ScummVM bug; I'll try recreating it as soon as possible.

Basically the game does not progress to the last act (Act IV), and this may be because of me solving the puzzles in a pretty random order.
You're tasked with finding several items that defines a hero, and one of these is Camel-Flage (or camouflage). In the game it's soot scraped of a wall, but the item you receive is not the actual hero item until you use it in your inventory, turning it to a pile of soot.
The thing is I forgot to do this and carried the soot around in my bag, unused. When I had all items, Act IV would not start and after using the soot it still did not start after swapping zones. Unfortunately I'd saved not far back, making it impossible to attempt to recreate or avoid the bug.

I do have a save from mid-game I'll boot up and rig to fail. I'll return as soon as I have attempted to recreate the bug (or get past the section, if it's common in ScummVM)!


Edit: I managed to get all the way to the end this time; I saved the "sword that goes ting" for last and was greeted with Act IV. However, the game mechanics broke down after this, as the huge dragon was nowhere to be found, rendering the final act unplayable. I'll do a new attempt tomorrow, this time trying to recreate the problem with the soot and Act IV not starting. I'll also copy the saves to my computer and attempt to finish it here, as it may be a N900 issue.