gamebin: The original Rainbow Six had dozens of bugs in it. For instance, while playing on Elite for mission 2, the terrorists would kill the hostages as soon as my team left the helicopter. Fun times. :-)
Now that's truly Elite...
I can't seem to find any information on this bug popping up in the original.
I think I have to accept mission 05 (to me) is broken (and thus the game) as, beside hostages, about half the terrorists also disappear en reappear between playthroughs. And apparently you have to kill all to advance.
There seems to be a 50/50 chance that a problematic 'Tango' will be rendered (on the currently selected resolution) and it happens consequently with about 4 or 5 of them in this mission which makes the chance of all of them being there very, very slim.
The original Rainbow Six is a great game concept-wise, but bugs like these make it a waste of money.