I doubt it's a Sierra related issue. I am running BIAB 146 on El Capitan 10.11.6. I downloaded your .MGU file from Dropbox and see the same results (as you attached above) for the Coda symbols.

I tried DS al Coda on a new test file and got the same results. Broken.

(The missing letters in Title sub-fields can be easily fixed by just re-entering the missing letters.)