I had a similar issue like mighty. I use streamable too and i was able to fix the videos in my posts simply by updating the post (no changes other than adding a space somewhere and saving the changes). Not sure why this happens tho
I have opened up a ticket so our internal Web team can take a look into this.
I do know that recent-past issues entered in the forum by Ya_shi_shi were affected and they were able to upload the videos after doing something on their side. like magic!
But we will hopefully get this resolved as soon as possible so that uploading videos will be without issues