Broken pistons and misfiring?

Sorry, but this may be a multi-part request. Purchased the vehicle listed above (used) for my son last December. From day one Check Engine light was on but multiple checks and nothing diagnosed and was shown how to turn light off until, at one check, was told he was misfiring on two pistons.

About 2 months ago he was driving when two pistons shattered, destroying the engine. Bought a replacement 2012 Forester engine with 28,000 miles. Car seemed to be running okay, and now, after about 300 miles, the Check Engine light is on again. He stopped by an AutoZone for a diagnosis and was told it was misfiring on three pistons.

First, would there have been any signs that may have warned the pistons were about to shatter, or could it have just happened without warning? If so, there should have been any mechanical warnings (loud noise, etc.) Could someone have done something to have disguised the problem?

With the "new" engine indicating multiple misfires do we need to worry about having the same problem?

Lastly, the engine had a 60 day warranty. Should this be covered?

I appreciate any feedback you can offer.


Thank you,
James Pruitt