Pedro,
Sorry to hear that your troubles didn't go away. It's hard to see much by looking at the pictures. In the picture where the short tooth is just engaging, it looks like the next pointy tooth is trying to get into the same notch. If that's happening, it seems like it would cause a jam-up right at the start of the kick then let go once past that point. But, you ground down that tooth, so hard to say if it would look the same now.
As for your match-up of quadrant to pinion, it seems to me that that shouldn't cause a problem because your pinion is more pointy than square. In looking at pinions that are out there, I am seeing what looks like three types: really flat tops (completely wrong); pointy, like your quadrant; and, just slightly flattened (like your pinion). I think this "just slightly flattened" type is probably still the right fit for your quadrant and it was just the way they made the gear as an aftermarket part. If someone else knows the "for certain" correct story on this, now would be a good time to chime in.
I was thinking about what Muskrat said about over-tightening the nut and squashing the sleeve. I would think that would not cause jamming in the downstroke, but might cause the lever to not return for the next kick (sometimes I need more than one
).
Other thoughts: How confident are you regarding everything inside the gearbox?; something in the primary like rubbing nut (as mentioned) or super over-tight chain; etc. I am running out of ideas (because of my limited knowledge, of course). I wish I could run down to Mexico to help you work it out. Not saying that would solve the problem, but we could have some good times with cerveza.
Richard L.