Some of the engine sounds posted on the DLS for the NYCTA trains also has this issue. I also encountered the problem with the doors. It seems the sound files for when the CHN coaches load or unload are converted to a format that TS12 or TS MAC seems to have trouble with.
I don't know about TS MAC but what I did was re-convert all the sound samples into the same type, perhaps changing the bit rite to something lower or higher. That fixed the problem entirely. But I think it should be looked into more.
