Twitch is giving us data, so it’s not that there’s a problem on our end, but an issue on their’s. Not that I don’t have faith in Twitch, but when I find a vendor has an issue I always assume it’ll never be fixed, just for due diligence.
You’ll want to just favor user IDs more than usernames, and use the user ID to get the username later. This is redundant and sucks to have to do, but ultimately it’s all we can do until we hear back. 