Product and version:
FileMaker Pro Advanced 14.0.3
OS and version:
Mac OS X El Capitan
When logging into a solution with multiple External Data Sources, the dialog box to login to the other FM databases show up blank. Just a white screen... which then freezes FileMaker and forces the user to force quit the application.
Have a FM db with just a guest account. Have an External Data Source with a FM file that has no guest account.
The only workaround is the open the other External Data Source files first then open the other FileMaker file.