Nice catch!

You got any insights on the stack size? We just might give it some more margin. Can we add a second fixture with multiple different contract instantiations?

I enabled heap and stack checks and allocations logging to see the issue root cause.
what sort of test would you like to have

C1 -> new C2() -> new C3() -> new C4() -> new C5()
or
contract C
{
  constructor() {
    new C1();
    new C2();
    new C3();
    new C4();
    new C5();
  }
}

what sort of test would you like to have

Can you add both? 🙂

Finally I decided to add a test:

  constructor() {
    new C1();
    new C2();
    new C3();
    new C4();
    new C5();
  }

they are both very similar in this context