Doubt about rings in piston

Good morning, I was recently maintaining my diesel engine because I had the loss of power and threw the oil through the rod, indicating decompression in the engine, so I decided to change the pistons and rings respectively.

I have put it again and continue giving me the same problem, I have tried two different brands of rings and pistons in this order

first assembly: New Teikin pistons, TP rings
- again gave the initial problems, it was decided to change the rings brand (appearance of recent failures, 100km approx)
second assembly: the same Teikin pistons, Npr Rings
- Rings Npr - Occasion, the turner said it could be a factory failure in the pistons (after the settlement of the rings appeared)
Third assembly: pistons were changed to some of Alfin coating (Teikin equally), TP rings

again gave again that problem of the oil, I am that I go crazy with this engine and the truth is that I want to know what would be their opinion about the true failure, the suppliers and the mechanic Without problems, others say that this behavior is completely normal for the oil rod, others say it can be a failure in the measurements of the rings sought and others say that it can be a second failed lot

attached photos of the third assembly