Test case:

import std.typecons;

class C { int i; byte b; }

void main()
{
  auto sa = [scoped!C, scoped!C];
  assert(cast(size_t)&sa[0].i % int.alignof == 0);
  assert(cast(size_t)&sa[1].i % int.alignof == 0); // fails
}

The problem is that the payload is declared as
private ubyte[__traits(classInstanceSize, T)] Scoped_store = void;
in std.typecons.scoped, as discussed at https://github.com/D-Programming-Language/phobos/pull/148#issuecomment-1590157 .