This seems to be happen all of a sudden to more posters,
It would be good to know, if this is only happening with certain system versions, or if it is a general problem.
I recently migrated two machines: Migration Assistant worked well on the first machine, when I used it immediately during the initial setup, when first prompted, if I want to migrate from a different computer. On the second machine our engineer had already set up the system, before I rceived the machine. Launching Migration Assistant separately to migrate the contents later caused all kinds of trouble.
- Time Machine would not accept the new computer as a replacement of the old and I had to start a complete new backup.
- And the instruments library was not migrated, like you observed.