I thnk the underlying issue could be the lack of swap when booting from ISO combined with the necessary space needed to hold a an squashed filesystem of more than 2gb in-memory. That is somewhat impossible with 2gb ram.
Most installer images are way beyond 2gb today.
I remember the general test recommendation for virtualbox being 2vcpu and 2gb ram.
But then - at that time - we tried to keep the images at max 2gb.
I even think there is a test script which creates a vm with 2gb ram and 10gb disk.