How to tell which nechanic is at fault

I had a shop rebuild my transmission and at times
it still shifts hard and its still under warranty and i
know when bolting trans into flywheel it has to
align perfectly or will not operate properly and ither
mechanic changed rotors calipers oil and oil filter
he says its the other guy who did something wrong
but he only drained 3 quarts out of motor when he
changed oil and added 6.5 quarts of 5w20 and
when truck messed up the tire locked up and then
a loud knocking started as the tire started working
and the motor mount was found broken and oil is
all over the bottom of transmission pan engine
drive shaft etc and rear end is leaking now but this
truck ran better than any truck i kno of not one light
or code was on and it has been taken care of and
the 190k miles are easy hwy and interstate miles
and never ticked or knocked , it was a great motor
then it just started knocking so loud. I just dont see
it it happening for no reason other than the wear
and tear something made it start in my opinion but
what?