Finally some thoughts about the reason can you give some more explanation about your thoughts?
BTW, the ringgaps are bigger now when I meassure them at the ridgearea, almost double.
Per
Given the ridge that shows now, it would seem that the pistons were installed without sufficient clearance and they expanded when they warmed up and knocked the "tooth" off the cross hatch to make their own clearance. An examination of the rings by a professional engine builder would probably answer the question.
It may be the machine shop may have tried to use the hone to obtain the clearance and this is always a bad idea. This usually results in the "teeth" being folded over which prevents the rings from seating properly.
But, in this case, I would guess that the pistons clearanced themselves by knocking the metal off the cylinder walls.
In the cases that people try to blame on the oil being too slick, the teeth are simply folded over by the excessive honing and are burnished by the rings, but the crosshatch is still visible.
Modern rings take a much smoother bore finish than the old non coated iron or chrome ring, but, as Cudamaan stated, the honing must be done properly.
I think the machine shop screwed up and no matter what kind of oil was used, the result would have been the same.