So... finally received the Tracker back from Taurus. They said they replaced the entire trigger mechanism. A quick inspction revealed new color coded springs so I assumed the rest was new as well.
I went to the range last Friday and using double action trigger pull: out of the first 14 rounds (two cylinders worth), it failed to fire twice. It then went on to fire the next 34 rounds in the box.
The FTF's felt exactly as it did before I sent the gun out, as though the hammer released early without enough oomph to ignite the primer.
My purpose for the .357 4" Tracker was purely defensive. Can't have a defensive weapon fail to fire... ever! Sold it at a gun show, today! Swore I'd never buy another Taurus (owned three... had problems with all three.)