Hi Andrew,
thanks for your reply.

I have version 2018 build 267 and running on MacOSX 10.14.6 with 2 user accounts, (my own main admin account plus a guest a\c for my wife which never gets used anyway)

I have checked my BIAB song folder and I have only the one song file (i.e. MySong.SGU) and while I do have external drives for storage and backup, I do not save my songs on external drives.

I will download the update you have linked and get back to you with what happens next.