Locking central differential?

I purchased a 2011 Subaru Impreza Outback Sport
in Sept. On day 4 of owning it, something happened
while diving on the interstate and it felt like I just
rear ended someone. The one car slammed with a
huge noise from the tranny and it felt like you just
hit a speed bump going 65. It went to the dealer.
Wouldn’t repeat. Did it the next morning on my way
to work and almost caused me to crash. The dealer
came and picked it up. A week later it did it with
them. This continued and I called in Subaru Corp
who came in, drove the car and had it happen, they
replaced the transmission. 72 days later I got my
car back. 3 weeks later, at its first oil change I’ve
had to do on it, I ask my mechanic about a light
tapping noise when the RPMs drop and it has a
loose rod and needs a new engine. Now nobody
wants to fix it. The dealer states it’s unrelated. The
last time they gave me the car when it hadn’t been
properly fixed, it locked up on the interstate at 75
and I lost control and spun off the road. That’s when
I called corporate.  It felt like I hit something and the
back end swung around. I’ve told this to everyone
and they still don’t feel like a loose rod and shaved
piston metal in the oil filter are from damage
sustained when the tranny locked.  Dispite the
shattered timing belt cover that’s against the engine
block. This car has had less that 3k miles since the
timing belt and water pump were replaced when I
purchased the car from the dealer.  It only has 75k
on it. Anybody know anything I don’t?