There is no magic to this. To me there are a few possibilities - first make absolutely sure that the nuts are not still bottoming out.

Make sure that the washers are not collapsing or digging into the rim causing looseness potentially coupled with nuts being too long.

My primary thought is that either your lug nuts or studs are yielding because they are crap material or have been over-torqued. First thing to do is to inspect the nuts and studs to see if you can see then distorting. Also insect the nuts to see if they have adequate thread engagement.

I remember back in the 80's my rear wheel fell off in my 69 Dart with Cragar wheels - fortunately no damage. I think I forgot to tighten the nuts.