In SimContests, Video does not not get processed

When setting up a video competition, the video can be uploaded and the accepted.
However, on the next page, the video processing spinner just goes round and round and the video processing never finishes.
In the back end admin, it initially show that the video entry has been created, including video thumbnails.
When you refresh the page, the entry disappears and we get a message saying " entry no longer exists"
FFMpeg settings are the same as those used for easysocial, which processes videos without any issues.