Here is an old video of Yonkata. Not a bad example at all. I particularly like their interpretation of the first two techniques. Very similar to some ideas that Henry Copeland showed us at a Yonkata seminar a couple of years ago. I also like the (fast) pacing of this demo.
But the reason that I posted it is as an example of the first ushirowaza that we played with this past weekend, which is the seventh technique from this collection appearing between time 0:20 and 0:22. This is a good example of what I was mentioning in my previous post about it being very difficult to prevent release #1, even if uke gets behind you.
Later in this exercise (technique #14, time 0:52-0:55) you see this idea repeated. Tori tries to do #1 release from an ushiro condition but uke succeeds at preventing R1, so tori slips under the arm (release #5) and finishes with maeotoshi.