Miss labeling of tv shows

I have the following problem with NCIS.
For some reason Plex has decided to create random NCIS icons on the TV show Tab for NCIS. I have Season 1 to 12 are OK.
Season 13 is problematic.
It has episodes 1- 15 in the correct folder on Plex.
Episode 16 has its own Icon in Plex
Episodes 17 & 18 Have own Icon in Plex
Episodes 19 & 20 Have own Icon in Plex
Episodes 21 & 22 Have own Icon in Plex

Each season and episode follows the following protocol
\NCIS\Season NN\SSSEEE Episode.Extension
eg
\NCIS\Season 13\S13E01 Stop the Bleeding.mkv
This is the same for every season and episode. As below

Try renaming your files in this fashion: ShowName Episode Name - sXXeXX. So in this case they would look like (NCIS.Personal Day.S13E02.mp4). I have all of mine labeled like this and have no issues. There is more information on naming episodes here.

Your naming should work,so I would check for incorrect embedded metadata as they are MP4s

How do you check for incorrect embedded metadata on a file?

on a Mac you can use iTunes
on Windows there is mp3tag

Many thanks to all suggestions. Problem seems to have disappeared of its own accord.