Thanks, so far I haven't been able to produce that segfault, so hopefully fixed.
I noticed that the documentation for frame-visible-p says:
"If FRAME is a text terminal frame, this always returns t.
Such frames are always considered visible, whether or not they are
currently being displayed on the terminal."
I could see that prior to tty child frames that was necessarily true, but now we have tty child frames shouldn't that documentation be updated? (I'm assuming at the code level it's no longer true since posframe hides it's frames by simply making them invisible).
Cheers,
Len.