Search with TheTVDB show ID instead of the title, 73069 for Kung Fu. See this example from another thread.
Also, changing the agent to The Movie Database in the search window may help when performing a Fix Match.
I ran a quick test on my system. Plex initially matched Kung Fu to Kung Fu Killer. I performed a Fix Match using TheTVDB ID. Plex found the match, downloaded correct cover art, episode titles, etc.
Plex occasionally has problems matching some TV shows, especially those with reboots, spinoffs, or a name similar to other shows. There is a new TV scanner/agent under development that will hopefully improve such situations.
