In Mafia Game 115, there was a confirmed (dead) tracker going into Day 3 MyLo with 6 players.

pandabear10 was the 1-Shot Bulletproof, but he claimed Doctor in order to both confirm himself (as there were no other PRs to counterclaim him) and try and draw a Mafia night kill.Town then subsequently no-lynched, however, knittingfrenzy18 was killed instead of pandabear10, who was attempting to draw the night kill.

However, the mafia eventually found that pandabear10 was indeed not a Doctor, and went on to win the game.

It is worth noting that, in a Matrix6 game, with a confirmed tracker early on in the game, it is possible to claim either Doctor or 1-Shot Bulletproof Townie and neither of the two can be counterclaimed by either faction, as both setups are identical with the exception of the protective role, as they are:

3. 5 Vanilla Townies, 1 Town Doctor, 1 Town Tracker, 2 Mafia Goons
6. 5 Vanilla Townies, 1 1-Shot Bulletproof Townie, 1 Town Tracker, 2 Mafia Goons