Hi!
I don't see this behaviour, however I run 10.10.
There has been some work done in this area -- Can you try this on development version of 25.1 and see if the problems exists there? (A "nightie" from
http://emacsforosx.com/builds would do.)
If you still get the crash, can you run it under "gdb" to see where the crash occurs?
-- Anders
Ps. I noticed a regression between 24.5 and 25.1. When the second frame is closed, the first is incorrectly placed, it is placed too low in what appears to be the height corresponding to a menu bar (which obviously isn't present).