I'm not the one who locked it, but I think the reason was to prevent additions based on unreliable sources. Can you post here the sources you want to use? Thanks.

Just IMDB. I thought that most of info comes from there. I have no personal knowledge.

I temporarily changed the TV status to "Returning Series" to unlock the ability to add new seasons. Did you need anything else?

edit: We usually recommend using official sources instead of other user-generated databases. You should be aware that all databases have slightly different guidelines. For example, we always add the episode in the original airing order and try to follow the original seasons. IMDb and Wikipedia sometimes chose to display the episodes in an alternative order (production, DVD, etc.). Also, user-generated is only as reliable as the user who made the edits. So some IMDb series have very good data, and other have terrible data. Since it's an old series I wouldn't worry too much about finding an official source. But I would recommend comparing the data of the main databases to see if there are any irregularities.

Great, thanks