Hello. This is fixed now and I am no longer able to replicate this issue. Thank you for the patience.
We have been working on improving support for playback on the the React Native platform and a recent change in the code in how Stream manages captions had caused caption requests to return 401 HTTP status codes. We have just rolled back this change and will make sure to take steps to test playback when captions are enabled specifically with videos with signed-urls. Videos without signed-urls turned on was not affected by this bug.