I have found a weird bug after choosing to play with music turned off. I like the soundtrack but get a different feel playing without it. If I have music turned off in settings, in the levels McCall and McCall 1, the game gets severely laggy and McCall's talking has no audio or speech bubbles, then it gets stuck! When this happens, after exiting, I still have to clear XIII from task manager or the game won't start again without rebooting. Took a while to figure out the issue, but it runs with no issue with music turned on, lags badly with it off! The rest of the levels are fine with music off. So I just set music to on before playing those 2 levels. I have the GOG version with unofficial 1.4.2 patch on Windows 10 64bit, this happens with or without the patch. Posting here in case anyone else has the same issue, I couldn't find anything online about it, so this could be useful to someone, you never know!