The question / the problem is this:
The processing of videos doesn’t work, since yesterday (approx 8 hours ago). Either this happens after uploading (both long and short videos):

  1. a message: “Error processing videos” (where the process is stucked, and at the same time one cannot delete it and/or 2. the process just gets stucked, it shows “Processing…”, and after that it persists (I have a number of such “Processing…” since yesterday, these processes still processing …).
    What may have happened? Does anyone know?

If this is promoted video via video.twitter.com then this may be related RESOLVED Incident: [2016-05-13] New promoted video uploads are unable to process successfully

Having the same issue today. Video is stuck in processing.