Files not added to index if sample is in the title

If the word sample is in the name (perhaps only if it is the first word) it is never added to library when the libraries get scanned.

Example:

File name “003-Sample REST Service.mp4” is not index. If I change it to “003-Example REST Service.mp4” it gets indexed.

That is expected.
https://support.plex.tv/articles/201381883-special-keyword-file-folder-exclusion/

You might want to change the scanner of this library from ‘Plex Movie Scanner’
to ‘Plex Video Files Scanner’