I have watched 3 episodes of the TV show Zinba but when I go to the progress tab it says I have only watched 1 episode.
Here is the show on TMDB: https://www.themoviedb.org/tv/93580-zinba/season/1?language=en-US
Because it counts only aired episodes. It is the progress of all aired episodes. If the release date is missing you could add them easily on TMDB 
The episode air dates for Zinba were never saved and are lost. Can you add a feature to add episodes without an air date to the progress tab?
No, because future aired episodes are also not count. Users want to see the progress on the current aired episodes.
Please, contribute the release dates if available. They will not be removed without a reason.
Some TV shows have episode release dates that are unavailable. Shows like Zinba and Another Life are cancelled shows but the episode release dates are unknown.
The progress tab says I have watched all of these episodes but I have only watched a few of them.