OK, lets start with the top ring. Based upon accepted standards for ring end gaps, based upon bore diameters: Most piston ring manufacturers recommend a minimum end gap of .004 inches times the bore diameter for the top piston compression ring. So for a 4 inch bore, the standard end gap would be .016 inches. As you have an 85.5 mm, or 3.366 inches. Using the suggested rule of thumb, which would work out at 0.004 X 3.366 = 0.013 inches, or 0.33 mm. So that ring gap is way too wide.
Mahle, the makers of these pistons have published ring end gap guidelines for the 2.5 and 2.7L M96 engines:
Mahle
Top ring-0,15...0,35mm....006"-.014"
2nd ring-0,60-0,80mm....024"-.032"
oil control-0,50-0,75mm...020"-.030"
Again, your gaps appear excessive. Overly large ring end gaps can cause a myriad of issues, from compression loss to oil consumption, and most importantly, excessive piston rock in the bore, which can result in ring land (the piston metal that separates the rings from each other) failures.
When a piece of ring land material breaks loose, it can get wedged between the piston and cylinder wall, stressing both. I would not be surprised to find that if you pulled the pistons out, you would find multiple ring land failures. I also noticed from your assembly photos that there were significant gaps between the rings and the cylinder walls, indicating oval cylinder liners, which would also exacerbate that piston rocking problem even more.
Lawyers often like to say that, "the devil is in the details". That is also very true for engine assembly.