^
You wrote:
I'm having a number of problems with old MGU files (created by 2012 or earlier versions).
Could you upload a couple of those files ?
Incidentally sending the Apple crash logs and offending MGU files goes to some dark room in Apple land never gets a response or answer. However there is an Apple forum/discussion group that may be able to figure out your crash log.
https://discussions.apple.com/welcomeyou have to sign in : look in the upper left hand corner for sign in and if this is the first time joining the group you have to provide an email contact ( i forget the details now since it has been a while since i first joined that group however i do use them frequently ).