Surface vanishes when join command is run

Hi
V5
taken from an object which was fine, then I moved a few surface edges with moveEdge, and joined, and had naked dot at ‘A’.
I explode the object,
I copy paste the surfaces forming this area out to a new file, and when I join them the rear vertical surface vanishes.
It doesnt do so in the source file.

what is wrong with it ?

and why naked dot at ‘A’ ?

Furthermore we all know nakedEdge will show on the edges of all this, where is the option to ignore outer edges of a surface joined but not made into an object solid ?
to have 43 showing and have to ‘next’ each time to get to the joined edges is annoying.

Surface vanishes when join.3dm (124.8 KB)

Cheers

Steve

Hello- Extract that face, RebuildEdges, Join it back.

-Pascal