This is a duplicate of 6x15 Bullet With My Name On It. This correction has been submitted to TVDb, but they refuse to remove it.
The official Homicide Hunter website lists the correct episode information:
https://www.investigationdiscovery.com/tv-shows/homicide-hunter-joe-kenda/?seasonId=57bf0bb56b66d144780dd7a8
There is no such episode as "My Rookie Mistake", this is a repeat of the episode 15 "Bullet with my name on it". There are only 20 episodes in season 6.
Shout by TheNightWolfBlockedParent2022-08-09T22:24:30Z
This episode is at least now the correct title, however Trakt.tv still has an episode 21 which there isn't one. Yet they even title it with the same name as this episode. Trakt.tv please remove S06E21 as it doesn't exist!