I've read the forums and did some investigating of my own and found the following to correct the issue of missing movie files but may be a challenge for those of us with huge personal media libraries (NAS-network attached system).
To maximize easy transfer and scrapes of your movies into XBMC or KODI, verify the following:
1. There is no spell check when saving movies to your hard drive of NAS, so compare your save movie titles to IMDb, Wiki or other movie source for the correct title usage. I've found the use of numeric vs roman numerals, punctuations of hyphens, apostrophes and commas sometime make a big difference.
2. Should you include the (year) as part of your title, verify the correct year as some foreign release are different from the year release in USA. Although the year is optional, it help differentiate movies with multiple reboots (i.e. Godzilla the span from 1954 to present or The Planet of the Apes, etc)
3. Be sure there are no punctuations are used at the end of a title that don't have one. Exceptions (UP!, Fire Up! vs FRANK or Grease), but check IMDb or other source to compare.
4. Lastly, should you have subtitles for foreign films, either in a separate folder or next to the actual movie file - the titles must match to ensure proper integration when viewing your movie.
This may be common sense or a no brain'er to some, and a pain in the rear to others. However, with a home media collection over 3 thousand and growing my task was daunting. Especially when 865 movies didn't show up in my KODI Library and there was a special request to view a classic it was frustrating to say the least.
After two weeks of work later and ALL of my movies of every genre are found and my KODI no longer have COOTIES
Now I take in-home movie requests as usual with flawless presentation.
Attention to detail now and you too will have a cootie-free KODI.
