i was working thru the issue today and it looks like the problem is on blizzards side. seems the crash happens when i post a wm_size message to the classic window, but before it has logged in. the crash points to referencing a memory address of 0xffffffffffff ... which is usually an uninitialized pointer or member variable.
i was able to reach out to a friend @ blizzard and he's going to see if they'll look into it. hopefully they can spot the bug quickly and push a patch for the following tuesday update.
if not i'll have to rework the maximize section.
until then, it looks like the work around is to log into your wow accounts then maximize the clients.
if anyone has anything else, please feel free to drop me a note.
i'm usually on discord during the day and pop in & out of the solid ice discord channel answering posted questions and chatting with any that need a hand. the discord info should be on the contact page at the bottom of the site.