[bug] filtering results by "music only" returns an empty "items" array (Piped Testing API only)

[Bellisario]

Official Instance

• [X] The bug is reproducible on the official hosted instance, or is API-related.

Describe the bug

Using the music_songs filter on Piped API, it returns a "successful" response with no result (the items array is empty).

This issue is only present on Piped Testing server, while the "main" instance seems to work correctly (when it works).

To Reproduce

1. Open this URL (testing instance): https://pipedtestingapi.kavin.rocks/search?q=queen&filter=music_songs
2. items array, containing all results, is empty
3. Open this URL (main instance): https://pipedapi.kavin.rocks/search?q=queen&filter=music_songs
4. (if the instance works) items array contains all the results as expected

This also works on the instance website: choosing filter "YT Music: Songs" on the testing instance, results on an infinite loader, while on the main instance all works as expected.

Expected behavior

• The items array should contain the results and should not be empty.
• The instance website should not show an infinite loader and should load results correctly.

Logs/Errors

The response of the API is 200, meaning the server "thinks" all it's working as expected.

There is no error on the API and on the instance website.

Browser, and OS with Version.

Not applicable. This issue is a server side issue.

Additional context

I noticed Piped was not working while developing my player, Musicale.\ After finding Piped was having a problem and there was a testing server working as expected, I decided to switch temporarily the API endpoint to make my player work again, but there was another problem, the issue above.

[Bnyro]

Likely that's just a side effect of being ratelimited now, they seem to block the access to more and more parts of YouTube from time to time when being rate limited.

EDIT: Ah, just saw Kavins comment on the other issue, so the above statement is likely not the case.

[Bnyro]

It could also be some A/B testing by YouTube though, that only affects certain regions.