Probably not a Drone issue, but I’m not sure where to post this and y’all are geniuses. 
I have the episode ‘After’ listed as Season 5, and as I have Drone to only search for current seasons, it missed the S04E09 After.
To me, sounds like Drone is doing what it’s told, but that maybe trakt or tvdb is screwy.
Season 4 looks to be the latest season of The Walking Dead, Trakt shows season 5 for some reason, but I think thats wrong and should correct itself when it refetches from tvdb.
Earlier, some one jumped the gun and added season 5 over at TVDB to 'The Walking Dead". Trakt picked this up. Looks like it has been correct on both TVDB and Trakt. Things should correct themselves when Nzbdrone updates the tv series.