@divemaster5734 said:
TMDB Quit Updating
TMDB has been working flawlessly on Kodi for over a year.
Then yesterday all my watched checks are gone from both movies and and TV shows.
After watching a show in a series I'll hold down to mark as watched, the check will appear, then disappear.

Does your Kodi import data from your Watchlist on TMDB?
Or is this information added by you directly to your Kodi?

I reloaded Diggz, and went through reauthorizations. Now when I try to make as watched I get TMDB ID 1402. A check mark will appear for a moment, then disappear. All the previous episodes from every show or movie I've ever watched is now gone.

I realized I didn't answer your question. If I let the show run out to the end it will usually automatically indicate watched, perhaps not immediately. I usually fast foreword throughout the show and rarely watch the credits, preferring to back out, mark as watched, and go to the next in the series. Hopefully this answers your question. Thank you, Brian

@divemaster5734 said:
I realized I didn't answer your question.
If I let the show run out to the end it will usually automatically indicate watched, perhaps not immediately.
I usually fast foreword throughout the show and rarely watch the credits, preferring to back out, mark as watched, and go to the next in the series.
Hopefully this answers your question.
Thank you,
Brian

I believe I understand.
You must be using a third-party program.
Diggz Xenon Kodi Build
In this case we cannot help.
Better to seek help on the Kodi Forum or with the App developers.