The coordinated failures implied by a failure of QEC to scale would be new physics; the existing principles don't predict that anything like that should occur.
Which isn't to say that it's impossible, but it would be quite exciting if it were the case.
Not really, no. If the breakpoint for fault tolerance is reached, then in the absence of new physics causing the noise that needs to be corrected to be adversarially coordinated, quantum computers are scaleable.
Which isn't to say that it's impossible, but it would be quite exciting if it were the case.