Windows and Doors Becoming Transparent (and other problems)

I don't know about the invisible doors and windows, never had that happen. The problem with your new house not immediately showing up on the old lot until you zoom in is a rendering issue, I believe, and an old, old problem that still happens to me sometimes. Very common but a bit of a pain. I usually go into the lot, delete a bit of fence, add it back and go out. The "new" house will then stay a while. But it hasn't happened to me in a long time.