2003 Pontiac Montana broken piston ring #6 cyl

A couple of years ago I had to have the intake manifold gasket replaced which was due to the problem with the original factory antifreeze, cost me $1200 as it was out of the 3 yr warranty though well under the milage warranty, no policy adjustment from GM.
Now my daughter has the car and in the middle of a 400 mile return trip the engine quit, towed in 200 miles and the GM dealer says the engine needs to be replaced as the 36 cyl piston ring broke and scored the bore. My question, is this failure caused in anyway by the previous intake manifold leak or repair of same, and if not what would cause the piston ring to fail?