Videos not uploading; all previously uploaded videos are gone

I’m experiencing an issue where uploading videos no longer works; the GET media/upload (STATUS) requests gives us back a 400 response even when the videos fit the Twitter guidelines. I would guess that this problem started happening within the past month, although it might have started several months ago.
This problem may or may not be related, but I have also noticed that every single single video we’ve uploaded through the API is now gone. This spans across multiple Twitter accounts we help manage. The text of the Tweet remains, as do photos and link attachments, but all videos are gone.
For reference, here is an example of a tweet from January of this year where we uploaded a video through the API, but as of today the video is now gone, and only the text remains:
I’m wondering if something related to our consumer key + API key has been “blacklisted” (we realized fairly recently that we’ve been hitting many rate limit requests). However, it’s only video uploads and old video tweets that seem to be having issues, and our rate limit errors were not related to video uploads or POST-ing any Tweets.
Any information on what could be causing this video-related issues?
Note: Uploading/Tweeting directly through Twitter is ok, and those videos are still up. All other API calls we make to post and get Tweets still work fine. Picture media works just fine.

Find any fix for this? Our videos only have been failing recently too. Pictures work fine, and the status posts just without video. Never had this issue before.