If the mower is not cutting level, it is anyone's guess why, if it appears adjusted properly.
You state TSC picked it up with a fork lift, that is the first mistake.
What else was bent/damaged beside the deck, is again a roll of the dice.
is it lift brackets? is the frame of the mower bent? was it previously damaged in transit? all unanswered questions.
Cutting to the chase,( no pun intended) TSC is liable to make it right, as they were the ones we assume, damaged it, but that is an assumption, no one has a crystal ball and without setting it on a jig checking various parts against a drawing of specifications everything is a guess.
If it were me, I would elevate the situation to the top people at TSC first. If the situation is not taken care of, then move on to an elevated case at Cub Cadet, as it actually could be a manufacturing snafu. The "authorized repair facility" just puts on new parts that they think might be the problem. In the mean time you have no use of the lawnmower.
if all this fails, then legal action needs to be started.
But, it should not have to go this far as the mower does not function as intended.
I'd be going back to TSC as they do have a 100% customer satisfaction policy.
They need to pick up the mower and drop off a completely new one that has not been damaged in any way, with no cost to you!
You are the injured party here, not the bad guy who drove it off a cliff.
(which at this point prolly sounds very inviting)
But this is just my thoughts -----