Sante Fe stops

What engine do you have? I don't see any TSB's for stalling, but there are some issues pertinent to certain engines which could contribute.

The six cylinder.

Do you have the 2.7 or the 3.5?

Thye only thing I see for the 2.7 is a TSB relating to "intermittent hesitation." When I first learned of this issue (prior to the TSB being issued), Hyundai referred to it as "very infrequent engine cutout" and described it as feeling a jerk while driving because the cutout was so momentary. They didn't (and won't) share the specific conditions which must be met for the stalling to occur, so I don't know whether it's possible for it to occur at a stop. I'd think it's a longshot, but I don't see anything else to point my finger at either. Most likely, it'll require a technician to experience and diagnose the condition while it's occurring.

My wife took it in and they said it needed a new "oxygen sensor"

Mine stopped on me while waiting for red lights of two different occasions.