Also for each conversion there are 2 part entries. you've changed one part.
The second part entry would look like:
[J:\Videos\TV\The Rifleman\Season 04\The Rifleman-S04E21-Two Ounces of Tin.mp4]
Which need to be changed to:
[F:\Videos\TV\The Rifleman\Season 04\The Rifleman-S04E21-Two Ounces of Tin.mp4]
If both parts are not changed in sync it'll crash the engine when trying to looking for the second part.