Pretty sure when I installed my friend's delta joints, it was an extremely tight fit. I think what we did was put the 2 inner washers in at the same time by greasing them up and wedging them in. Basically, we installed the 2 green washers, then got at least a tapered edge of the the red washers in the spaces. From there we were able to slowly wedge or forcefully move them into place.
If you install 3 and then try to get that last one in by itself, you'll run into the issue you're experiencing where there's no room for it. We also didn't put the bolt through until everything lined up first.