I know it would be crossing geography here, but there was an odd sounding "bell" on 2 of the NYC models from several years back (R11 and R34).
While this sound was (to the best of my knowledge) correct for these, it is an odd sound that is really nothing like a bell. It almost sounds like the cyclic buzz of an alarm on a clock radio (what most of us used (or still do) before everyone used their phone to make various sounds for their alarms 
).
I have no idea if this is the same sound, or if it's possible for the sound set bell to be accidentally recorded for an incorrect engine when the other sounds like the station stops are correct. That's an MTH question. Maybe at the manufacturing level there is a "piecing together" of the various elements before they create the master sound file.
Thought it might be worth a mention, just in case.
-Dave
