@ethicians said:
Keys from append_to_response sometimes not included in the response
I'm using append_to_response to retrieve recommendations and external_ids for TV Shows.
Using the exacly same API calls, I notice that sometimes these keys aren't returned in the response, causing my app to throw an error on the missing keys. I've seen old posts that mention this similar problem:

https://www.themoviedb.org/talk/5f7c2f533e2ec80037d9ee60
https://www.themoviedb.org/talk/673beac177eb59f2f01a6674

Example of API request:

https://api.themoviedb.org/3/tv/1402?api_key=xxx&append_to_response=recommendations,external_ids

Is this a known issue?

I just tested it and received all the data.
I don't recall any other user complaining about this.

In what scenarios might these keys not be included in the response?

I believe that when the data does not exist in the Database.

I think it's one of those bugs that occasionally occur and the programmers never figure out the source. :-)